essay about 2011 japan earthquake and tsunami

Japan earthquake & tsunami of 2011: Facts and information

The Great Tohoku earthquake destroyed more than 100,000 buildings and triggered a nuclear disaster.

A surprise disaster

The 2011 tohoku earthquake, early warning, death toll of the 2011 earthquake and tsunami, the fukushima nuclear meltdown, the response, worldwide effects, amazing facts, additional resources, bibliography.

The Japan earthquake and tsunami of 2011, also known as the 2011 Tohoku earthquake and tsunami or the Great Tohoku earthquake, was a natural disaster that shook northeastern Japan on March 11, 2011. The disaster began when a magnitude-9 earthquake shook the region in the early afternoon, unleashing a savage tsunami.

The effects of the great earthquake , which was the strongest in Japan's recorded history, were felt around the world, from Norway's fjords to Antarctica 's ice sheet. Tsunami debris has continued to wash up on North American beaches years later.

In Japan, residents are still recovering from the disaster. As of November 2021, there were still about 39,000 evacuees who lost their homes; 1,000 of them were still living in temporary housing, according to Japan's Reconstruction Agency .

More than 120,000 buildings were destroyed, 278,000 were half-destroyed and 726,000 were partially destroyed, according to the agency. The direct financial damage from the disaster is estimated to be about $199 billion dollars (about 16.9 trillion yen), according to the Japanese government. The total economic cost could reach up to $235 billion, the World Bank estimated, making it the costliest natural disaster in world history.

Related: How Japan's 2011 Earthquake Happened

The unexpected disaster was neither the largest nor the deadliest earthquake and  tsunami  to strike this century. That record goes to the 2004 Banda Aceh earthquake and tsunami in Sumatra, a magnitude-9.1, which killed more than 230,000 people. But Japan's one-two punch proved especially devastating for the earthquake-savvy country, because few scientists had predicted the country would experience such a large earthquake and tsunami.

Japan's scientists had forecast a smaller earthquake would strike the northern region of Honshu, the country's main island. Nor did they expect such a large tsunami. But there had been hints of the disaster to come. The areas flooded in 2011 closely matched those of a tsunami that hit Sendai in A.D. 869. In the decade before the 2011 Tohoku earthquake, a handful of Japanese geologists had begun to recognize that a large earthquake and tsunami had struck the northern Honshu region in that year. However, their warnings went unheeded by officials responsible for the country's earthquake hazard assessments, Live Science previously reported. Now, tsunami experts from around the world have been asked to assess the history of past tsunamis in Japan, to better predict the country's future earthquake risk.

"For big earthquakes, the tsunami is going to be the big destructive factor," said Vasily Titov, director of the National Oceanic and Atmospheric Administration's Center for Tsunami Research in Seattle, Washington told Live Science. "But if the nation is prepared, warning and education definitely saves lives. Compare the human lives lost in Sumatra and Japan. It's about 10 times less."

The 2011 Tohoku earthquake struck offshore of Japan, along a subduction zone where two of Earth's tectonic plates collide. In a subduction zone, one plate slides beneath another into the mantle, the hotter layer beneath the crust. The great plates are rough and stick together, building up energy that is released as earthquakes. East of Japan, the Pacific plate dives beneath the overriding Eurasian plate. The temblor completely released centuries of built up stress between the two tectonic plates, a recent study found.

The March 11 earthquake started on a Friday at 2:46 p.m. local time (5:46 a.m. UTC). It was centered on the seafloor 45 miles (72 kilometers) east of Tohoku, at a depth of 15 miles (24 km) below the surface. The shaking lasted about six minutes. 

Scientists drilled into the subduction zone soon after the earthquake and discovered a thin, slippery clay layer lining the fault, according to a 2013 study in the journal Science . The researchers think that this clay layer allowed the two plates to slide an incredible distance, some 164 feet (50 meters), facilitating the enormous earthquake and tsunami. 

Residents of Tokyo received a minute of warning before the strong shaking hit the city, thanks to Japan's earthquake early warning system. The country's stringent seismic building codes and early warning system prevented many deaths from the earthquake, by stopping high-speed trains and factory assembly lines. People in Japan also received texted alerts of the earthquake and tsunami warnings on their cellphones.

The number of confirmed deaths is 19,747 as of December, 2021, according to the reconstruction agency. More than 2,500 people are still reported missing.

Less than an hour after the earthquake, the first of many tsunami waves hit Japan's coastline. The tsunami waves reached run-up heights (how far the wave surges inland above sea level) of up to 128 feet (39 meters) at Miyako city and traveled inland as far as 6 miles (10 km) in Sendai. The tsunami flooded an estimated area of approximately 217 square miles (561 square kilometers) in Japan, according to the National Oceanic and Atmospheric Administration .

The waves overtopped and destroyed protective tsunami seawalls at several locations. The massive surge destroyed three-story buildings where people had gathered for safety. Near Oarai, the tsunami generated a huge whirlpool  offshore, captured on video.

The tsunami caused a cooling system failure at the Fukushima Daiichi Nuclear Power Plant , which resulted in a level-7 nuclear meltdown and release of radioactive materials. The electrical power and backup generators were overwhelmed by the tsunami, and the plant lost its cooling capabilities.  

"Fukushima was created by the tsunami. The earthquake was not a factor," Titov said. "Fukushima was designed for a tsunami smaller than the one we saw."

Very low levels of radioactive chemicals that leaked from Fukushima have been detected along the North American coast offshore Canada and California. Trace amounts of cesium-134 and cesium-137 (radioactive isotopes) were found in seawater collected in 2014 and 2015, Live Science reported at the time .

In the tsunami's aftermath, Japan's Meteorological Agency was criticized for issuing an initial tsunami warning that underestimated the size of the wave. In some regions, such as Miyagi and Fukushima, only 58% of people headed for higher ground immediately after the earthquake, according to a Japanese government study published in August 2011. Many people also  underestimated their personal risk , or assumed the tsunami would be as small as ones they had previously experienced, the study found.

Scientists from around the world descended on Japan following the earthquake and tsunami. Researchers sailed offshore and dropped sensors along the fault line to measure the forces that caused the earthquake. Teams studied the tsunami deposits to better understand ancient sediment records of the deadly waves. Earthquake engineers examined the damage, looking for ways to build buildings more resistant to quakes and tsunamis. 

"The tsunami itself died out a long time ago, but the effects in Japan will be there for decades," Titov told Live Science.

— The biggest earthquakes in history

— The 10 worst U.S. natural disasters

— Image gallery: This millennium's destructive earthquakes

The tsunami waves also traveled across the Pacific, reaching Alaska, Hawaii and Chile. In Chile, some 11,000 miles (17,000 km) distant, the tsunami was 6.6 feet (2 meters) high when they reached the shore, according to the Pacific Tsunami Warning Center. 

Related: Weird Earth Movement After Japan Earthquake Finally Explained

The surge of water carried an estimated 5 million tons of debris out to sea, the  National Oceanic and Atmospheric Agency reported . Japanese docks and ships, and countless household items, have arrived on U.S. and Canadian shores in the ensuing years. The U.S. Coast Guard fired on and sank the derelict boat 164-foot Ryou-Un Maru in 2012 in the Gulf of Alaska. The ship started its journey in Hokkaido. 

Here are some of the amazing facts about the Japan earthquake and tsunami.

• The earthquake shifted Earth on its axis of rotation by redistributing mass, like putting a dent in a spinning top. The temblor also shortened the length of a day by about a microsecond.
• More than 5,000 aftershocks hit Japan in the year after the earthquake, the largest a magnitude 7.9.
• About 250 miles (400 km) of Japan's northern Honshu coastline dropped by 2 feet (0.6 meters), according to the U.S. Geological Survey.
• The jolt moved Japan's main island of Honshu eastward by 8 feet (2.4 m).
• The Pacific Plate slid westward near the epicenter by 79 feet (24 m).
• In Antarctica, the seismic waves from the earthquake sped up the Whillans Ice Stream, jolting it by about 1.5 feet (0.5 m).
• The tsunami broke icebergs off the Sulzberger Ice Shelf in Antarctica.
• As the tsunami crossed the Pacific Ocean, a 5-foot high (1.5 m) high wave killed more than 110,000 nesting seabirds at the Midway Atoll National Wildlife Refuge.
• In Norway, water in fjords pointing toward Japan sloshed back and forth as seismic waves from the earthquake raced through.
• The earthquake produced a low-frequency rumble called infrasound, which traveled into space and was detected by the Goce satellite.
• Buildings destroyed by the tsunami released thousands of tons of ozone-destroying chemicals and greenhouse gases into the air.
• How to Build an Emergency Survival Kit
• Red Cross Tsunami Survival Guide
• Ready.gov – What To Do During An Earthquake

Vasily Titov, Chief Scientist of the National Oceanic and Atmospheric Administration's (NOAA) Center for Tsunami Research in Seattle, Washington.

“Status of Reconstruction and Reconstruction Efforts.” Japan Reconstruction Agency, Dec. 2021. https://www.reconstruction.go.jp/english/

P.M. Fulton et al. “Low Coseismic Friction on the Tohoku-Oki Fault Determined from Temperature Measurements,” Science, Vol 342, Dec. 2013. https://www.science.org/doi/10.1126/science.1243641

NOAA/ National Weather Service U.S. Tsunami Warning System. https://www.tsunami.gov/

Japan Tsunami Marine Debris. NOAA Marine Debris Program. https://marinedebris.noaa.gov/disaster-debris/japan-tsunami-marine-debris

This article was updated Feb. 11, 2022 by Live Science Senior Writer Brandon Specktor.

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

32 scary parasitic diseases

Orcas have attacked and sunk another boat in Europe — and experts warn there could be more attacks soon

Newfound 'glitch' in Einstein's relativity could rewrite the rules of the universe, study suggests

Most Popular

• 2 China creates its largest ever quantum computing chip — and it could be key to building the nation's own 'quantum cloud'
• 3 MIT gives AI the power to 'reason like humans' by creating hybrid architecture
• 4 'Quantum-inspired' laser computing is more effective than both supercomputing and quantum computing, startup claims
• 5 2,500-year-old Illyrian helmet found in burial mound likely caused 'awe in the enemy'
• 3 Atoms squished closer together than ever before, revealing seemingly impossible quantum effects
• 4 Sun launches strongest solar flare of current cycle in monster X8.7-class eruption

HISTORIC ARTICLE

Mar 11, 2011 ce: tohoku earthquake and tsunami.

On March 11, 2011, Japan experienced the strongest earthquake in its recorded history.

Earth Science, Oceanography, Geography, Physical Geography

Loading ...

Learning materials.

• Click below to see a MapMaker Interactive map displaying tectonic activity surrounding the Tohoku earthquake and tsunami.

On March 11, 2011, Japan experienced the strongest earthquake in its recorded history. The earthquake struck below the North Pacific, 130 kilometers (81 miles) east of Sendai, the largest city in the Tohoku region , a northern part of the island of Honshu.

The Tohoku earthquake caused a tsunami . A tsunami—Japanese for “ harbor wave ”—is a series of powerful waves caused by the displacement of a large body of water. Most tsunamis, like the one that formed off Tohoku, are triggered by underwater tectonic activity , such as earthquakes and volcanic eruptions . The Tohoku tsunami produced waves up to 40 meters (132 feet) high, More than 450,000 people became homeless as a result of the tsunami. More than 15,500 people died. The tsunami also severely crippled the infrastructure of the country .

In addition to the thousands of destroyed homes, businesses, roads, and railways, the tsunami caused the meltdown of three nuclear reactors at the Fukushima Daiichi Nuclear Power Plant . The Fukushima nuclear disaster released toxic , radioactive materials into the environment and forced thousands of people to evacuate their homes and businesses.

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Last Updated

October 19, 2023

User Permissions

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.

If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.

Text on this page is printable and can be used according to our Terms of Service .

Interactives

Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources

An official website of the United States government

Here's how you know

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

On This Day: 2011 Tohoku Earthquake and Tsunami

On March 11, 2011, a magnitude (Mw) 9.1 earthquake struck off the northeast coast of Honshu on the Japan Trench. A tsunami that was generated by the earthquake arrived at the coast within 30 minutes, overtopping seawalls and disabling three nuclear reactors within days. The 2011 Tohoku Earthquake and Tsunami event, often referred to as the Great East Japan earthquake and tsunami , resulted in over 18,000 dead, including several thousand victims who were never recovered.

The deadly earthquake was the largest magnitude ever recorded in Japan and the third-largest in the world since 1900. 

How It Happened

The 2011 event resulted from thrust faulting on the subduction zone plate boundary between the Pacific and North America plates, according to the U.S. Geological Survey .

This region has a high rate of seismic activity, with the potential to generate tsunamis. Past earthquakes that generated tsunamis in the region have included the deadly events of 1611 , 1896 , and 1933 .

The March 11, 2011 earthquake generated a tsunami with a maximum wave height of almost 40 meters (130 feet) in the Iwate Prefecture . Researchers also determined that a 2,000-kilometer (1,242-mile) stretch of Japan’s Pacific coast was impacted by the tsunami.

Following the earthquake, a tsunami disabled the power supply and cooling of three Fukushima Daiichi reactors, causing a significant nuclear accident . All three nuclear cores largely melted in the first three days. 

As of December 2020, the Japan National Police Agency reported 15,899 deaths, 2,527 missing and presumed deaths, and 6,157 injuries for the Great East Japan event.

In Japan, the event resulted in the total destruction of more than 123,000 houses and damage to almost a million more. Ninety-eight percent of the damage was attributed to the tsunami. The costs resulting from the earthquake and tsunami in Japan alone were estimated at $220 billion USD. The damage makes the 2011 Great East Japan earthquake and tsunami the most expensive natural disaster in history. 

Although the majority of the tsunami’s impact was in Japan, the event was truly global. The tsunami was observed at coastal sea level gauges in over 25 Pacific Rim countries, in Antarctica, and on the west coast of the Atlantic Ocean in Brazil.

The tsunami caused $31 million USD damage in Hawaii and $100 million USD in damages and recovery to marine facilities in California. Additionally, damage was reported in French Polynesia, Galapagos Islands, Peru, and Chile. 

Fortunately, the loss of life outside of Japan was minimal (one death in Indonesia and one death in California) due to the Pacific Tsunami Warning System and its connections to national-level warning and evacuation systems. 

From Peril to Preparedness

To learn from the tragedy in Japan, researchers collected extensive data on tsunami wave forces and building performance. This facilitated improvement in tsunami mitigation strategies, such as building codes. Over 6,200 tsunami wave measurements were collected in Japan and the Pacific region. 

Several thousands of lives across the world were lost to large, far-afield tsunamis prior to the establishment of the Pacific Tsunami Warning System in 1965. The Great East Japan earthquake and tsunami demonstrated that despite the severity of the natural hazard the investment in the warning system has been a success. 

Japan is often considered the country most prepared for tsunamis but still lost numerous lives in this event. Nonetheless, experts believe many lives were saved in Japan and elsewhere due to the existing warning and mitigation systems.

An effective tsunami warning system relies on the free and open exchange and long-term management of global data and science products to mitigate, model, and forecast tsunamis. NCEI is the global data and information service for tsunamis. Global historical tsunami data, including more information about the Great East Japan earthquake and tsunami, are available via interactive maps and a variety of web services.

For more information on how you can prepare for a tsunami, visit the National Tsunami Hazard Mitigation Program . Also, visit NCEI’s Natural Hazards website for more earthquake and tsunami data, images, and educational materials.

Kong, L., P. Dunbar, and N. Arcos (2015). Pacific Tsunami Warning System: A Half-Century of Protecting the Pacific 1965-2015. Honolulu: International Tsunami Information Center.

Satake, K. (2014). Chapter 24, The 2011 Tohoku, Japan, Earthquake and Tsunami. Extreme Natural Hazards, Disaster Risks and Societal Implications, Cambridge University Press, p. 340-351.

UNESCO/IOC (2012). Summary Statement from the Japan - UNESCO - UNU Symposium on The Great East Japan Tsunami on 11 March 2011 and Tsunami Warning Systems: Policy Perspectives 16 - 17 February 2012

Broken links updated.

Related Links

Article tags, related news.

August 25, 2023

On This Day: 2009 Samoa Islands Tsunami

August 16, 2023

On This Day: Historic Krakatau Eruption of 1883

March 3, 2023

A ship washed ashore during the 2011 Japan tsunami lies amidst wreckage in Kesennuma, Miyagi, Japan.

The 2011 Japan Tsunami Was Caused By Largest Fault Slip Ever Recorded

Clay lubricated the fault zone in the Japan trench, producing the devastating tsunami, researchers say.

The largest fault slip ever recorded produced the devastating 2011 Japan tsunami , according to three studies published today.

Two years ago, the sea off the coast of Japan reared up and swept away   tens of thousands of lives in a devastating natural disaster.

The 2011   earthquake has been the subject of intense study ever since, and the trench that produced it is the best studied in the world. (See " Japan Tsunami: 20 Unforgettable Pictures .")

Now, three papers published today in the journal   Science reveal the magnitude 9 earthquake off the east coast of Japan still has the capacity to surprise.

Experts calculate the fault—or the boundary between two tectonic plates—in the   Japan trench slipped by as much as 164 feet (50 meters). Other similarly large magnitude earthquakes, including the 9.1 Sumatra event in 2004, resulted in a 66-to-82 foot (20-to-25 meter) slip in the fault.

"We've never seen 50-meter [slips]," said Kelin Wang, a geophysicist with the   Geological Survey of Canada in British Columbia.

The next largest slip would probably be the Chile earthquake in 1960, said Wang, who was not involved in the research. Based on the limited data recorded from that earthquake, the fault slipped by 98 to 131 feet (30 to 40 meters).

Most of the movement occurred horizontally, he explained. But because the plates are wedged together at this trench, that horizontal displacement still managed to thrust up enough seawater to produce the killer tsunami that hit Japan.

Greasing The Wheels

Lubrication, specifically involving clay, is the key to such massive movement, said   Frederick Chester , a geophysicist at Texas A & M University in College Station, and lead author of   one of the studies .

The two tectonic plates involved are the Pacific plate, on which the Pacific Ocean resides, and a portion of the North American plate ,   on which parts of Japan sit.

A thick layer of clay sits atop the Pacific plate, which is getting dragged under a portion of the North American plate. As the Pacific plate dives into a trench off the coast of Japan, small portions of the clay get smeared along the plate boundary, Chester explained.

That clay traps water, rendering it quite slippery, he said. "We think that's responsible for allowing the incredibly large slip we observed near the trench."

Normally, when two plates collide, there is friction. You can think of friction like a brake, Chester explained. "But clay almost removes any braking properties."

Not a Lot of Heat

The unprecedented data haul that enabled Chester and colleagues to figure out what happened during the 2011 earthquake is courtesy of a rapid response by the Japan Agency for Marine-Earth Science and Technology, said   Emily Brodsky , a geophysicist at the University of California, Santa Cruz, and a co-author of one of the studies.

The   Japan Trench Fast Drilling project enabled researchers to get out to the fault zone about a year after the earthquake and drop instruments down to measure temperature anomalies—the sudden slips during an earthquake can generate vast amounts of heat—and to bring up samples of the fault zone itself for analysis.

Experts were able to take core samples of sediment and rock from the trench—located in 23,000 feet (7,000 meters) of water—thanks to a sophisticated drilling ship.

"[This] was right at the edge of what engineering could do," Brodsky said.

Not only did they find evidence of this thin layer of lubricating clay, but experts were also able calculate how much heat and friction was involved.

Even though the earthquake produced a 1,100° to 2,200°F (600° to 1,200°C) temperature increase, the amount of friction that had to be overcome to produce the fault slip wasn't as large as researchers expected, said Brodsky.

This helped confirm the fact that something else was going on—namely the clay lubrication.

It's difficult to say whether something like this could happen elsewhere, said Wang, because no other submarine trench has as many instruments monitoring it.

"Nowhere else do we have such a massive monitoring system."

Follow Jane J. Lee on Twitter .

For Hungry Minds

Related topics.

• EARTHQUAKES

You May Also Like

Japan's 2011 megaquake left a scar at the bottom of the sea. Scientists finally explored it.

What causes earthquakes?

3,600-year-old tsunami ‘time capsule’ sheds light on one of humanity’s greatest disasters

A tsunami could wipe this Norwegian town off the map. Why isn’t everyone leaving?

A huge volcano near Naples has been convulsing. What does it mean?

• Environment
• Perpetual Planet

History & Culture

• History & Culture
• History Magazine
• Mind, Body, Wonder
• Paid Content
• Terms of Use
• Privacy Policy
• Your US State Privacy Rights
• Children's Online Privacy Policy
• Interest-Based Ads
• About Nielsen Measurement
• Do Not Sell or Share My Personal Information
• Nat Geo Home
• Attend a Live Event
• Book a Trip
• Inspire Your Kids
• Shop Nat Geo
• Visit the D.C. Museum
• Learn About Our Impact
• Support Our Mission
• Advertise With Us
• Customer Service
• Renew Subscription
• Manage Your Subscription
• Work at Nat Geo
• Sign Up for Our Newsletters
• Contribute to Protect the Planet

Copyright © 1996-2015 National Geographic Society Copyright © 2015-2024 National Geographic Partners, LLC. All rights reserved

• Election 2024
• Entertainment
• Newsletters
• Photography
• Personal Finance
• AP Investigations
• AP Buyline Personal Finance
• AP Buyline Shopping
• Press Releases
• Israel-Hamas War
• Russia-Ukraine War
• Global elections
• Asia Pacific
• Latin America
• Middle East
• Election Results
• Delegate Tracker
• AP & Elections
• Auto Racing
• 2024 Paris Olympic Games
• Movie reviews
• Book reviews
• Personal finance
• Financial Markets
• Business Highlights
• Financial wellness
• Artificial Intelligence
• Social Media

Timeline of Japan’s 2011 quake, tsunami and nuclear disaster

FILE - In this March 14, 2011, file photo, evacuees rest in a shelter in Soma city, Fukushima prefecture, Japan, three days after a massive earthquake and tsunami struck the country’s north east coast. A hydrogen explosion occurs at the Fukushima Daiichi nuclear plant’s No. 1 reactor, sending radiation into the air. Residents within a 20-kilometer (12-mile) radius are ordered to evacuate. Similar explosions occur at two other reactors over the following days. (AP Photo/Wally Santana, File)

FILE - In this Feb. 9, 2017, file image released by Tokyo Electric Power Company (TEPCO), a remote-controlled “cleaning” robot, bottom, enters the reactor containment chamber of Unit 2 for inspection and cleaning a passage for another robot as melted materials at Fukushima Daiichi nuclear power plant in Okuma town, Fukushima prefecture, northeastern Japan. (TEPCO via AP, File)

FILE - In this March 15, 2011, file photo, a Japanese survivor of an earthquake and tsunami rides his bicycle through the leveled city of Minamisanriku, Miyagi prefecture, northeastern Japan. March 11, 2021 marks the 10th anniversary of the massive earthquake, tsunami and nuclear disaster that struck Japan’s northeastern coast. (AP Photo/David Guttenfelder, File)

FILE - In this Feb. 16, 2016, file photo, a worker, wearing protective suits and masks, takes notes in front of storage tanks for radioactive water at the tsunami-crippled Fukushima DaiIchi nuclear power plant, operated by Tokyo Electric Power Company (TEPCO) in Okuma town, Fukushima Prefecture, northeastern Japan. A government panel recommends the controlled release into the sea of rapidly increasing amounts of leaked radioactive cooling water at the Fukushima plant. (Toru Hanai/Pool Photo via AP, File)

FILE - In this March 11, 2011, file photo, earthquake-triggered tsunami sweeps shores along Iwanuma, Miyagi prefecture, northern Japan. March 11, 2020 marks the 10th anniversary of a massive earthquake, tsunami and nuclear disaster that struck Japan’s northeastern coast. (Kyodo News via AP, File)

FILE - In this Feb. 14, 2021, file photo, portion of a highway is blocked by a landslide after an earthquake hit Soma, Fukushima prefecture, northeastern Japan. The magnitude 7.3 earthquake hit off the Fukushima coast, causing minor damage at the Fukushima Daiichi nuclear plant. (Hironori Asakawa/Kyodo News via AP, File)

FILE - This March 13, 2011, file photo, Unit 1 reactor, left, of the Fukushima Daiichi nuclear power plant with its top part of walls blown off after an explosion is seen with other units including Unit 3 reactor, second from right, where a hydrogen explosion could occur in Okuma town, Fukushima Prefecture, Japan. A magnitude 9.0 earthquake strikes off the coast at 2:46 p.m., triggering a towering tsunami that smashes into the nuclear plant, destroying its power and cooling systems and triggering meltdowns at three reactors. (Masaru Nishimoto/Kyodo News via AP, File)

FILE - This March 15, 2011, file image made available from Tokyo Electric Power Company (TEPCO) via Kyodo News, shows the damaged No. 4 unit of the Fukushima Daiichi nuclear power plant in Okuma town, northeastern Japan. A magnitude 9.0 earthquake strikes off the coast at 2:46 p.m. March 11, 2011, triggering a towering tsunami that smashes into the nuclear plant, destroying its power and cooling systems and triggering meltdowns at three reactors. (TEPCO via Kyodo News, File)

FILE - In this April 7, 2011, file photo, an empty street runs through the deserted town of Minami Soma, Fukushima prefecture, Japan, inside the evacuation zone, established for the 20 kilometer radius around the Fukushima Daiichi nuclear reactors. A hydrogen explosion occurs at the Fukushima Daiichi nuclear plant’s No. 1 reactor, sending radiation into the air. Residents within a 20-kilometer (12-mile) radius are ordered to evacuate. Similar explosions occur at two other reactors over the following days. (AP Photo/David Guttenfelder, File)

FILE - In this April 7, 2011, file photo, dogs wander around a town of Minami Soma, inside the deserted evacuation zone established for the 20 kilometer radius around the Fukushima Daiichi nuclear power plant in northeastern Japan. A hydrogen explosion occurs at the plant’s No. 1 reactor, sending radiation into the air. Residents within a 20-kilometer (12-mile) radius are ordered to evacuate. Similar explosions occur at two other reactors over the following days. (AP Photo/Hiro Komae, File)

• Copy Link copied

TOKYO (AP) — Thursday marks the 10th anniversary of a massive earthquake, tsunami and nuclear disaster that struck Japan’s northeastern coast. Here is a timeline of events:

— March 11, 2011: A magnitude 9.0 earthquake strikes off the coast at 2:46 p.m., triggering a towering tsunami that reaches land within half an hour. The tsunami smashes into the Fukushima Daiichi nuclear plant, destroying its power and cooling systems and triggering meltdowns at three reactors.

— March 12: A hydrogen explosion occurs at the plant’s No. 1 reactor, sending radiation into the air. Residents within a 20-kilometer (12-mile) radius are ordered to evacuate. Similar explosions occur at two other reactors over the following days.

— April 12: Japan raises the accident to category 7, the highest level on the International Nuclear and Radiological Event Scale, from an earlier 5, based on radiation released into the atmosphere.

— April 24: The government designates a 2-kilometer (1.25-mile) exclusion zone around the nuclear plant spanning nine municipalities.

— Dec. 16: After workers struggle for months to stabilize the plant, Japan declares a “cold shutdown,” with core temperatures and pressures down to a level where nuclear chain reactions do not occur.

— July 23, 2012: A government-appointed independent investigation concludes that the nuclear accident was caused by a lack of adequate safety and crisis management by the plant’s operator, Tokyo Electric Power Co., lax oversight by nuclear regulators and collusion.

— April 1, 2014: The evacuation order is eased for a city west of the wrecked nuclear plant. Parts of at least eight other municipalities are allowed to reopen over the next three years, though the number of returnees remains low due to a lack of jobs and lingering radiation concerns.

— Dec. 22:TEPCO completes the removal of all spent nuclear fuel rods from the No. 4 reactor cooling pool, an initial milestone in the plant’s decades-long decommissioning.

— 2015-2019: Small robots equipped with cameras and sensors are sent into the damaged reactors but provide only limited views of the highly radioactive melted fuel debris. That makes plans for its removal more difficult.

— Feb. 10, 2020: A government panel recommends the controlled release into the sea of rapidly increasing amounts of leaked radioactive cooling water at the Fukushima plant. TEPCO says its 1.37 million ton storage capacity will be full in fall 2022.

— Dec. 10: Police say the death toll from the disaster, mostly from the tsunami, reaches 18,426, including 2,527 whose remains have not been found.

— Feb. 13, 2021: A magnitude 7.3 earthquake hits off the Fukushima coast, leaving one dead and injuring more than 180 people. It causes minor damage at the nuclear plant.

— March 6: Prime Minister Yoshihide Suga visits Fukushima and pledges to accelerate decontamination efforts so all remaining no-go zones can be reopened, but doesn’t give a timeframe.

• 0 Shopping Cart

Japan Earthquake 2011

Japan earthquake 2011 case study.

An earthquake measuring 9.0 on the Richter Scale struck off Japan’s northeast coast, about 250 miles (400km) from Tokyo at a depth of 20 miles.

The magnitude 9.0 earthquake happened at 2:46 pm (local time) on Friday, March 11, 2011.

The earthquake occurred 250 miles off the North East Coast of Japan’s main island Honshu.

Japan 2011 Earthquake map

Japan is located on the eastern edge of the Eurasian Plate. The Eurasian plate, which is continental, is subducted by the Pacific Plate, an oceanic plate forming a subduction zone to the east of Japan. This type of plate margin is known as a destructive plate margin . The process of subduction is not smooth. Friction causes the Pacific Plate to stick. Pressure builds and is released as an earthquake.

Friction has built up over time, and when released, this caused a massive ‘megathrust’ earthquake.

The amount of energy released in this single earthquake was 600 million times the energy of the Hiroshima nuclear bomb.

Scientists drilled into the subduction zone soon after the earthquake and discovered a thin, slippery clay layer lining the fault. The researchers think this clay layer allowed the two plates to slide an incredible distance, some 164 feet (50 metres), facilitating the enormous earthquake and tsunami .

2011 Japan Earthquake Map

The earthquake occurred at a relatively shallow depth of 20 miles below the surface of the Pacific Ocean. This, combined with the high magnitude, caused a tsunami (find out more about how a tsunami is formed on the BBC website).

Areas affected by the 2011 Japanese earthquake.

What were the primary effects of the 2011 Japan earthquake?

Impacts on people

Death and injury – Some 15,894 people died, and 26,152 people were injured. 130,927 people were displaced, and 2,562 remain missing.

Damage – 332,395 buildings, 2,126 roads, 56 bridges and 26 railways were destroyed or damaged. 300 hospitals were damaged, and 11 were destroyed.

Blackouts – Over 4.4 million households were left without electricity in North-East Japan.

Transport – Japan’s transport network suffered huge disruptions.

Impacts on the environment

Landfall – some coastal areas experienced land subsidence as the earthquake dropped the beachfront in some places by more than 50 cm.

Land movement – due to tectonic shift, the quake moved parts of North East Japan 2.4 m closer to North America.

Plate shifts – It has been estimated by geologists that the Pacific plate has slipped westwards by between 20 and 40 m.

Seabed shift – The seabed near the epicentre shifted by 24 m, and the seabed off the coast of the Miyagi province has moved by 3 m.

Earth axis moves – The earthquake moved the earth’s axis between 10 and 25 cm, shortening the day by 1.8 microseconds.

Liquefaction occurred in many of the parts of Tokyo built on reclaimed land. 1,046 buildings were damaged

What were the secondary effects of the 2011 Japan earthquake?

Economy – The earthquake was the most expensive natural disaster in history, with an economic cost of US$235 billion.

Tsunami –  Waves up to 40 m in high devastated entire coastal areas and resulted in the loss of thousands of lives. This caused a lot of damage and pollution up to 6 miles inland. The tsunami warnings in coastal areas were only followed by 58% who headed for higher ground. The wave hit 49% of those not following the warning.

Nuclear power – Seven reactors at the Fukushima nuclear power station experienced a meltdown. Levels of radiation were over eight times the normal levels.

Transport –  Rural areas remained isolated for a long time because the tsunami destroyed major roads and local trains and buses. Sections of the Tohoku Expressway were damaged. Railway lines were damaged, and some trains were derailed. 

Aftermath – The ‘Japan move forward committee’ thought that young adults and teenagers could help rebuild parts of Japan devastated by the earthquake.

Coastal changes – The tsunami was able to travel further inland due to a 250-mile stretch of coastline dropping by 0.6 m.

What were the immediate responses to the Japan 2011 earthquake?

• The Japan Meteorological Agency issued tsunami warnings three minutes after the earthquake.
• Scientists had been able to predict where the tsunami would hit after the earthquake using modelling and forecasting technology so that responses could be directed to the appropriate areas.
• Rescue workers and around 100,000 members of the Japan Self-Defence Force were dispatched to help with search and rescue operations within hours of the tsunami hitting the coast.
• Although many search and rescue teams focused on recovering bodies washing up on shore following the tsunami, some people were rescued from under the rubble with the help of sniffer dogs.
• The government declared a 20 km evacuation zone around the Fukushima nuclear power plant to reduce the threat of radiation exposure to local residents.
• Japan received international help from the US military, and search and rescue teams were sent from New Zealand, India, South Korea, China and Australia.
• Access to the affected areas was restricted because many were covered in debris and mud following the tsunami, so it was difficult to provide immediate support in some areas.
• Hundreds of thousands of people who had lost their homes were evacuated to temporary shelters in schools and other public buildings or relocated to other areas.
• Many evacuees came from the exclusion zone surrounding the Fukushima nuclear power plant. After the Fukushima Daiichi nuclear meltdown, those in the area had their radiation levels checked, and their health monitored to ensure they did not receive dangerous exposure to radiation. Many evacuated from the area around the nuclear power plant were given iodine tablets to reduce the risk of radiation poisoning.

What were the long-term responses to the Japan 2011 earthquake?

• In April 2011, one month after the event occurred, the central government established the Reconstruction Policy Council to develop a national recovery and reconstruction outlook for tsunami-resilient communities. The Japanese government has approved a budget of 23 trillion yen (approximately £190 billion) to be spent over ten years. Central to the New Growth Strategy is creating a ‘Special Zones for Reconstruction’ system. These aim to provide incentives to attract investment, both in terms of business and reconstruction, into the Tohoku region.
• Also, the central government decided on a coastal protection policy, such as seawalls and breakwaters which would be designed to ensure their performance to a potential tsunami level of up to the approximately 150-year recurrence interval.
• In December 2011, the central government enacted the ‘Act on the Development of Tsunami-resilient Communities’. According to the principle that ‘Human life is most important, this law promotes the development of tsunami-resistant communities based on the concept of multiple defences, which combines infrastructure development and other measures targeting the largest class tsunami.
• Japan’s economic growth after the Second World War was the world’s envy. However, over the last 20 years, the economy has stagnated and been in and out of recession. The 11 March earthquake wiped 5–10% off the value of Japanese stock markets, and there has been global concern over Japan’s ability to recover from the disaster. The priority for Japan’s long-term response is to rebuild the infrastructure in the affected regions and restore and improve the economy’s health as a whole.
• By the 24th of March 2011, 375 km of the Tohoku Expressway (which links the region to Tokyo) was repaired and reopened.
• The runway at Sendai Airport had been badly damaged. However, it was restored and reusable by the 29th of March due to a joint effort by the Japanese Defence Force and the US Army.
• Other important areas of reconstruction include the energy, water supply and telecommunications infrastructure. As of November 2011, 96% of the electricity supply had been restored, 98% of the water supply and 99% of the landline network.

Why do people live in high-risk areas in Japan?

There are several reasons why people live in areas of Japan at risk of tectonic hazards:

• They have lived there all their lives, are close to family and friends and have an attachment to the area.
• The northeast has fertile farmland and rich fishing waters.
• There are good services, schools and hospitals.
• 75% of Japan is mountainous and flat land is mainly found in coastal areas, which puts pressure on living space.
• They are confident about their safety due to the protective measures that have been taken, such as the construction of tsunami walls.

Japan’s worst previous earthquake was of 8.3 magnitude and killed 143,000 people in Kanto in 1923. A magnitude 7.2 quake in Kobe killed 6,400 people in 1995 .

Premium Resources

Please support internet geography.

If you've found the resources on this page useful please consider making a secure donation via PayPal to support the development of the site. The site is self-funded and your support is really appreciated.

Related Topics

Use the images below to explore related GeoTopics.

Previous Topic Page

Topic home, next topic page, share this:.

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)
• Click to share on Pinterest (Opens in new window)
• Click to email a link to a friend (Opens in new window)
• Click to share on WhatsApp (Opens in new window)
• Click to print (Opens in new window)

If you've found the resources on this site useful please consider making a secure donation via PayPal to support the development of the site. The site is self-funded and your support is really appreciated.

Search Internet Geography

Top posts and pages.

Latest Blog Entries

Pin It on Pinterest

• Click to share
• Print Friendly

Fault That Caused Japan’s 2011 Earthquake Is Thin and Slippery

A group of scientists drilled miles beneath the Pacific Ocean, uncovering conditions that made the Tohoku-Oki earthquake and tsunami so devastating

Sarah Zielinski

The magnitude 9.0 Tohoku-Oki earthquake that struck Japan on 11 March 2011, killing more than 15,000 people and setting off a devastating tsunami that the nation is still working to recover from , brought up a lot of troubling questions. For instance, what made such a powerful earthquake possible, and could it happen again in Japan or somewhere else?

An international group of scientists that drilled miles beneath the Pacific Ocean and into the earthquake fault now have answers to these questions, and they report their findings in a trio of papers published today in Science .

The epicenter of the 2011 quake was in an unusual spot , about 130 kilometers east of Sendai, Japan, just off the northern coast of that nation. In this area, a subduction zone, the Pacific plate is diving beneath the Eurasian plate. Strong earthquakes are possible here, but scientists hadn’t thought that there was enough energy to produce one larger than magnitude 7.5. They were wrong, and they’ve been interested in finding out more about what made the fault capable of producing such a large quake.

The epicenter of 2011 Tohoku-Oki earthquake was off the east coast of northern Japan. Image via USGS

A little over a year after the earthquake, the deep sea drilling vessel Chikyu was tasked with the mission to drill into the fault off the Japanese coast and install a temperature observatory. By taking the temperature of a fault after an earthquake, scientists can measure how much energy was released in the quake and calculate a fault’s friction—how easily the rocks rub against each other.

“One way to look at the friction of these big blocks is to compare them to cross-country skis on snow,” Robert Harris, a study co-author and geophysicist at Oregon State University, said in a statement . “At rest, the skis stick to the snow and it takes a certain amount of force to make them slide. Once you do, the ski's movement generates heat and it takes much less force to continue the movement…. The same thing happens with an earthquake.”

Getting that temperature measurement was tricky. The Chikyu team had to drill 850 meters into the seafloor, which itself was 6,900 meters below the ocean’s surface. They had to deal with bad weather, and the fault itself was still shifting, putting the instruments at risk.

The difficult work paid off, though, and it revealed residual heat from the earthquake, from which the scientists could calculate the fault's friction, which was very low. Bottom line: “The Tohoku fault is more slippery than anyone expected,” Emily Brodsky, a study co-author and geophysicist at the University of California, Santa Cruz, said in another statement .

The slippery nature of the fault helps to explain some characteristics of the 2011 quake. The fault slipped an unprecedented 50 meters and the rupture, which began deep underground, reached the surface where it caused a sudden disturbance in the ocean and set off the tsunami.

The drilling and laboratory tests also revealed another characteristic of the fault that made it so dangerous. The low friction can be attributed to incredibly fine clay sediment within the fault. “It's the slipperiest clay you can imagine,” Christie Rowe, a study co-author and geologist at McGill University, said in a statement . “If you rub it between your fingers, it feels like a lubricant.” Incidentally, the area between the Pacific and Eurasian plates that experiences slip is also very thin, less than five meters across, which would make it the thinnest known fault zone on the planet.

Measuring the earthquake’s thermal signal was a first for science. It “was a major accomplishment,” Harris said, “but there is still a lot we don't yet know.” For example, researchers don't yet know how generalizable these results are to other subduction zones across the world or what effect the thinness of fault zones has on earthquake hazards. Nonetheless, the drilling results “suggest that the shallow megathrust at the Japan Trench has special traits not seen in many other subduction zones,” Kelin Wang of Natural Resources Canada and Masataka Kinoshita of the Japan Agency for Marine-Earth Science and Technology—the agency that runs the Chikyu —wrote in an accompanying Perspectives article .

Similar conditions may be rare, but they do exist in some places of the north Pacific, such as the Kamchatka Peninsula in Russia and the Aleutian Islands in Alaska, notes Rowe.Deep sea drilling shows that these regions have that same usually slippery clay that lowered the friction in the Japan fault.

But the fact that the unusual circumstances of the Japan fault may be rare shouldn’t put scientists, or the public, at ease, Wang and Kinoshita say. Such huge, shallow slip isn’t necessary for a devastating tsunami to form, and it wasn’t what caused either the 2010 Chile tsunami that destroyed 370,000 homes or the 2004 Indian Ocean tsunami that killed nearly 230,000 people. "It's hard to say how generalizable these results are until we look at other faults," Brodsky added. "But this lays the foundation for a better understanding of earthquakes and, ultimately, a better ability to identify earthquake hazards."

The magnitude 9.0 Tohoku-Oki earthquake that struck Japan on 11 March 2011, killing more than 15,000 people and setting off a devastating tsunami that the nation is still working to recover from, brought up a lot of troubling questions. For instance, what made such a powerful earthquake possible, and could it happen again in Japan or somewhere else? An international group of scientists that drilled miles beneath the Pacific Ocean and into the earthquake fault now have answers to these questions, and they report their findings in a trio of papers published today in Science. The epicenter of the 2011 quake was in an unusual spot, about 130 kilometers east of Sendai, Japan, just off the northern coast of that nation. In this area, a subduction zone, the Pacific plate is diving beneath the Eurasian plate. Strong earthquakes are possible here, but scientists hadn’t thought that there was enough energy to produce one larger than magnitude 7.5. They were wrong, and they’ve been interested in finding out more about what made the fault capable of producing such a large quake. The epicenter of 2011 Tohoku-Oki earthquake was off the east coast of northern Japan. Image via USGS A little over a year after the earthquake, the deep sea drilling vessel Chikyu was tasked with the mission to drill into the fault off the Japanese coast and install a temperature observatory. By taking the temperature of a fault after an earthquake, scientists can measure how much energy was released in the quake and calculate a fault’s friction—how easily the rocks rub against each other. “One way to look at the friction of these big blocks is to compare them to cross-country skis on snow,” Robert Harris, a study co-author and geophysicist at Oregon State University, said in a statement. “At rest, the skis stick to the snow and it takes a certain amount of force to make them slide. Once you do, the ski's movement generates heat and it takes much less force to continue the movement…. The same thing happens with an earthquake.” Getting that temperature measurement was tricky. The Chikyu team had to drill 850 meters into the seafloor, which itself was 6,900 meters below the ocean’s surface. They had to deal with bad weather, and the fault itself was still shifting, putting the instruments at risk. The difficult work paid off, though, and it revealed residual heat from the earthquake, from which the scientists could calculate the fault's friction, which was very low. Bottom line: “The Tohoku fault is more slippery than anyone expected,” Emily Brodsky, a study co-author and geophysicist at the University of California, Santa Cruz, said in another statement. The slippery nature of the fault helps to explain some characteristics of the 2011 quake. The fault slipped an unprecedented 50 meters and the rupture, which began deep underground, reached the surface where it caused a sudden disturbance in the ocean and set off the tsunami. The drilling and laboratory tests also revealed another characteristic of the fault that made it so dangerous. The low friction can be attributed to incredibly fine clay sediment within the fault. “It's the slipperiest clay you can imagine,” Christie Rowe, a study co-author and geologist at McGill University, said in a statement. “If you rub it between your fingers, it feels like a lubricant.” Incidentally, the area between the Pacific and Eurasian plates that experiences slip is also very thin, less than five meters across, which would make it the thinnest known fault zone on the planet. Measuring the earthquake’s thermal signal was a first for science. It “was a major accomplishment,” Harris said, “but there is still a lot we don't yet know.” For example, researchers don't yet know how generalizable these results are to other subduction zones across the world or what effect the thinness of fault zones has on earthquake hazards. Nonetheless, the drilling results “suggest that the shallow megathrust at the Japan Trench has special traits not seen in many other subduction zones,” Kelin Wang of Natural Resources Canada and Masataka Kinoshita of the Japan Agency for Marine-Earth Science and Technology—the agency that runs the Chikyu—wrote in an accompanying Perspectives article. Similar conditions may be rare, but they do exist in some places of the north Pacific, such as the Kamchatka Peninsula in Russia and the Aleutian Islands in Alaska, notes Rowe.Deep sea drilling shows that these regions have that same usually slippery clay that lowered the friction in the Japan fault. But the fact that the unusual circumstances of the Japan fault may be rare shouldn’t put scientists, or the public, at ease, Wang and Kinoshita say. Such huge, shallow slip isn’t necessary for a devastating tsunami to form, and it wasn’t what caused either the 2010 Chile tsunami that destroyed 370,000 homes or the 2004 Indian Ocean tsunami that killed nearly 230,000 people. "It's hard to say how generalizable these results are until we look at other faults," Brodsky added. "But this lays the foundation for a better understanding of earthquakes and, ultimately, a better ability to identify earthquake hazards."

Get the latest Science stories in your inbox.

Sarah Zielinski | | READ MORE

Sarah Zielinski is an award-winning science writer and editor. She is a contributing writer in science for Smithsonian.com and blogs at Wild Things, which appears on Science News.

Japan earthquake: social aftershocks of Fukushima disaster are still being felt

Research Fellow in Human and Social Sciences, University of Southampton

Research Fellow in the Department of Sociology, University of Warwick

Disclosure statement

Becky Alexis-Martin receives funding from the Aged Veterans Fund. She is the Principal Investigator of the UK Nuclear Families project, and explores the social and cultural impacts of nuclear weapons testing. She works closely with the British Nuclear Test Veterans Association and the NCCF.

Thom Davies receives funding from the ERC, working on a project called 'Toxic Expertise' and has previously been funded by the Japanese Society for the Promotion of Science. He has conducted research in Fukushima and Chernobyl.

University of Warwick provides funding as a founding partner of The Conversation UK.

University of Southampton provides funding as a member of The Conversation UK.

View all partners

At 5.59am local time on November 22, Fukushima was hit by a 7.4 magnitude earthquake, triggering a tsunami warning. For residents in the same region of Japan devastated by the major 2011 Tōhoku earthquake and its tsunami, the threat of a renewed disaster was very real.

The tsunami warning was lifted a few hours later, and the earthquake was later declared a long-term aftershock from the larger quake five years ago. But for people still coming to terms with that disaster and its aftermath, this new earthquake will severely test their resilience once again.

On March 11 2011, the 9.0 magnitude earthquake created a 15-metre tsunami that inundated the Fukushima Daiichi (Fukushima I) nuclear power station. Power was disabled to three reactors, which caused a serious nuclear accident as cooling systems failed. Large quantities of radiation were immediately released into the environment and approximately 100,000 people were evacuated.

The long-term social consequences of the original Fukushima Daiichi accident have been broad and far-reaching . Perception of risk , the likelihood of exposure to danger, has been at the heart of social controversy after the 2011 disaster. Radiation is invisible, and it is challenging to understand or percieve a threat that can only be detected by specialist scientific equipment. Often women and children are hit the hardest by this, regardless of socioeconomic status.

The concept of Fūhyōhigai , or the “harmful rumour”, was initially used by the media and local government to dismiss local women’s concerns about radiation exposure as weak and unscientific. However, this led to a cultural shift by women known as Fukushima’s “radiation brain moms” , who purchased monitoring equipment and took matters into their own hands, forming citizen radiation monitoring organisations (CRMOs) .

By forming these groups of resistance, self-help and support, women rejected their culture’s social norms of obedience and subservience, that could have suppressed them from cultivating outrage over injustice and inequality. Participation in CRMOs has decreased over time, as the social memory of Fukushima Daiichi fades, but citizen science initiatives such as Safecast still provide useful information to many.

The recent earthquake temporarily halted the cooling system at the nearby Fukushima Daini (Fukushima II) reactor, and so there is likely to be a resurgence in monitoring, and a reunion of these support networks. Regardless of what happens now, there has already been a positive seismic shift in attitudes by both the government and scientists toward concerned mothers and community monitoring.

Living in ‘temporary’ permanence

Many impacts of the 2011 disaster have been hidden away in the private spaces of everyday life, with the tragedy putting enormous strain on family relations . Not only were thousands of families displaced from their homes, evacuation has meant the separation of family groups.

Where once three generations could live together in Fukushima’s close-knit rural villages, relocation to cramped prefabricated temporary housing has meant many are forced to live apart. Today, five years after the disaster, 174,000 people are still displaced in a state of “temporary” permanence. Disconnection from the familiarity of place and family, as well as the constant worry about radiation risk, even threatens marital relationships. “Atomic divorce” ( Genpatsu rikon ) is on the rise , with disagreements on radiation safety, or whether to relocate back to territory now deemed “decontaminated”. News of the recent earthquake will doubtless have jogged memories and resurfaced hidden tensions.

The Japanese government is gradually declaring sections of the 20km nuclear exclusion zone safe and habitable. Despite this, the desire to move back to previously contaminated land has been underwhelming . For example, four months after Naraha Town was declared safe in September last year, only 6% of former inhabitants decided to move home to one of Fukushima’s many atomic “ ghost towns ”.

In the town of Minamisōma, on the northern edge of the exclusion zone, thousands of mothers and children have refused to return , despite societal pressure not to “betray” their home communities.

Nuclear uncertainty

While Japan’s tsunami warning system worked well , there is still considerable uncertainty surrounding the consequences and likelihood of a further natural hazard causing a nuclear accident in Japan.

The 2011 Fukushima Daiichi accident had already permanently changed the Japanese nuclear landscape. The government has undergone a process of gradual nuclear decommissioning since October 2011, and Fukushima Daaichi and Dai-ni no longer produce energy. Yet, Japan is still heavily reliant on nuclear energy and since 2015 has restarted two of its nuclear reactors, with 24 other reactors in the process of restart approvals.

While social resilience to emergencies has improved since 2011 in Japan, the social aftershocks of Fukushima Daaichi are ongoing. Though many advances have been made that emancipate vulnerable populations and provide increased connectivity, it remains to be seen how much these new technologies and attitudes have improved social resilience and reduced the likelihood of anxiety within the community of Fukushima.

• Earthquakes
• Nuclear safety
• Japan earthquake

Compliance Lead

Lecturer / Senior Lecturer - Marketing

Assistant Editor - 1 year cadetship

Executive Dean, Faculty of Health

Lecturer/Senior Lecturer, Earth System Science (School of Science)

• Search Menu
• Volume 238, Issue 1, July 2024 (In Progress)
• Volume 237, Issue 3, June 2024
• Advance Access
• Applied and Marine Geophysics
• General Geophysical Methods
• Geodynamics and Tectonics
• Geomagnetism and Electromagnetism
• Gravity, Geodesy and Tides
• Heat Flow and Volcanology
• Rock and Mineral Physics, Rheology
• 100 Influential Papers
• Advance Articles
• Express Letters
• Hunga Volcano Special Issue
• East Anatolia Fault Special Issue
• Special Issues
• Why Publish
• Author Guidelines
• Submission Site
• Read & Publish
• Developing Countries Initiative
• Author Resources
• Self-Archiving policy
• Rights and Permissions
• About Geophysical Journal International
• Editorial Board
• About the Royal Astronomical Society
• About the DGG
• Journals on Oxford Academic
• Books on Oxford Academic

Article Contents

1 introduction, 2 interseismic plate-coupling inversion, 3 coupling-based earthquake scenarios, 4 tsunami simulations in the western indian ocean, 5 discussion, 6 conclusions, acknowledgements, data availability.

• < Previous

Constraints from GPS measurements on plate coupling within the Makran subduction zone and tsunami scenarios in the western Indian Ocean

• Article contents
• Figures & tables
• Supplementary Data

Guo Cheng, William D Barnhart, David Small, Constraints from GPS measurements on plate coupling within the Makran subduction zone and tsunami scenarios in the western Indian Ocean, Geophysical Journal International , Volume 237, Issue 1, April 2024, Pages 288–301, https://doi.org/10.1093/gji/ggae046

• Permissions Icon Permissions

Plate-coupling estimates and previous seismicity indicate that portions of the Makran megathrust of southern Pakistan and Iran are partially coupled and have the potential to produce future magnitude 7+ earthquakes. However, the GPS observations needed to constrain coupling models are sparse and lead to an incomplete understanding of regional earthquake and tsunami hazard. In this study, we assess GPS velocities for plate coupling of the Makran subduction zone with specific attention to model resolution and the accretionary prism rheology. We use finite element model-derived Green's functions to invert for the interseismic slip deficit under both elastic and viscoelastic Earth assumptions. We use the model resolution matrix to characterize plate-coupling scenarios that are consistent with the limited spatial resolution afforded by GPS observations. We then forward model the corresponding tsunami responses at major coastal cities within the western Indian Ocean basin. Our plate-coupling results show potential segmentation of the megathrust with varying coupling from west to east, but do not rule out a scenario where the entire length of the megathrust could rupture in a single earthquake. The full subduction zone rupture scenarios suggest that the Makran may be able to produce earthquakes up to M w 9.2. The corresponding tsunami model from the largest earthquake event ( M w 9.2) estimates maximum wave heights reaching 2–5 m at major port cities in the northern Arabian Sea region. Cities on the west coast of India are less affected (1–2 m). Coastlines bounding eastern Africa, and the Strait of Hormuz, are the least affected (<1 m).

The Makran subduction zone (MSZ) of Iran and Pakistan currently accommodates northward subduction of the Arabian oceanic plate beneath continental Eurasia at a rate of ∼3.5 cm yr −1 over the last 3 Ma (Kopp et al . 2000 ; DeMets et al . 2010 ; Smith et al . 2012 ; Fig.  1 ). The MSZ stretches approximately 1000 km from west to east and is bounded by strike-slip fault systems: the right-lateral Minab–Zendan fault to the west and the left-lateral Ornach-Nal and Chaman faults to the east. These two strike-slip systems separate the Makran region from active continent–continent collisions forming the Himalaya and Zagros Mountain ranges. The distance between the active trench and volcanic arc in the MSZ varies from 400 to 600 km, owing to a shallow subduction angle (<5°; Quittmeyer & Jacob 1979 ; Byrne et al . 1992 ; Regard et al . 2010 ; Barnhart et al . 2014 ; Hayes et al . 2018 ). The active convergence between the Arabian and Eurasian plates also produces the world's largest accretionary prism in the MSZ, the Makran accretionary prism, which is divided into a 100–150 km wide submarine portion and a 150–200 km subaerial portion from south to north, respectively (Burg 2018 ). The notable width of the emergent portion of the accretionary prism likely results from shallow angle subduction, exceptionally high incoming sediment thickness (up to 7.5 km) at the trench (Smith et al . 2012 ) and extensive sediment underplating, evidenced by reflection seismic data (Fowler et al . 1985 ; Platt et al . 1985 ; Kopp et al . 2000 ).

(a) Topographic and bathymetric map of the western Indian Ocean region. Orange stars indicate major coastal cities: MC: Muscat; CB: Chah Bahar; GW: Gwadar; PN: Pasni; OM: Ormara; KA: Karachi; ST: Surat; MB: Mumbai; ML: Mangalore; KZ: Kozhikode; KO: Kochi; KC: Kuwait City; DM: Dammam; DH: Doha; AD: Abu Dhabi; DB: Dubai; MO; Mogadishu; DS: Dar es Salaam; MP: Maputo; DN: Durban. (b) Regional seismicity ( M w 4.5+, 1905–2022) and simplified structural map of the Makran subduction zone, modified from Burg ( 2018 ). Three rectangles along the coastal Makran indicate maximum estimated rupture areas for historic earthquake events (Byrne et al . 1992 ). Plate motion of Arabia relative to Eurasia (AR:EU) is shown by the solid arrow (DeMets et al . 2010 ). Structures and images are overlain on SRTM15+ relief model (Tozer et al . 2019 ).

Historically, the MSZ shows relatively low seismicity rates in comparison to other subduction zones in the world (Heidarzadeh et al . 2008 ; Mokhtari et al . 2019 ). However, several significant earthquakes have been reported in the MSZ, some of which were tsunamigenic. According to Byrne et al . ( 1992 ), four large earthquakes ( M w  > 7.0) may have ruptured the plate boundary along the eastern part of the MSZ (Fig.  1 ), including the 1765 event that was felt strongly at Karachi in easternmost Makran, two coastal events in 1851 and 1864 affecting the town of Gwadar and the 1945 M w 8.0–8.3 event near Pasni that was followed by a large aftershock in 1947 to the south. The 1945 event is the largest instrumentally recorded earthquake in the subduction zone and is known to have caused a large tsunami, which is possibly the second deadliest tsunami event in the Indian Ocean basin killing over 4000 people (Heck 1947 ). The western section of the Makran, in contrast, has less documented seismic activity than the eastern MSZ and holds no clearly documented record of great subduction zone earthquakes. Only two events are reported to have occurred in the western Makran, in 1008 and 1483, but the latter event likely occurred within the Strait of Hormuz and thus may not be associated with megathrust rupture (Musson 2009 ; Rajendran et al . 2013 ). Additionally, some non-megathrust earthquakes of the Makran were tsunamigenic, such as the 2013 Baluchistan strike-slip earthquake ( M w 7.7), which triggered a landslide offshore Makran and led to a tsunami event (Baptista et al . 2020 ; Heidarzadeh & Satake 2015 ; Hoffmann et al . 2015 ).

Several megacities are located along the rim of the western Indian Ocean (Fig.  1 ). These cities include Mumbai (18+ million), Karachi (16+ million), Surat (6+ million), Dar es Salaam (6+ million), Mogadishu (2+ million) and major cities in the Persian Gulf (such as Dubai, Kuwait City and Doha, each with a population exceeding 2 million). Therefore, tsunamigenic earthquakes produced by the MSZ will potentially lead to high economic losses and human casualties in the western Indian Ocean, making assessment of the earthquake and tsunami potential of the Makran a critical component of regional risk analysis. Several plate-coupling models (i.e. the degree of interseismic strain accumulation) of the Makran have been proposed by previous studies. For example, Frohling & Szeliga ( 2016 ) found that the Makran megathrust is segmented, with a plate coupling of 58 per cent in eastern and western Makran, and a lower coupling ratio (31 per cent) along the central-western portion of the Makran. Lin et al . ( 2015 ) conducted Bayesian inversion of interferometric synthetic aperture radar (InSAR) observations from 2003 to 2010 for plate-coupling model in the eastern MSZ. They showed that high interseismic coupling occurs in the ruptured area of the 1945 M w 8.0–8.3 earthquake (Fig.  1 ), while lower coupling lies on both sides of the epicentral area. The inferred plate-coupling model may imply future occurrence of magnitude 7+ earthquakes, or a multisegment rupture event that would likely exceed magnitude 8 (Lin et al . 2015 ).

These previous plate-coupling studies in the MSZ invoked an elastic half-space mechanical model (Okada 1992 ), where the Earth behaves elastically during the interseismic period. However, in a viscoelastic Earth, the stresses induced by megathrust coupling are relaxed through viscous flow in the mantle during the decades to centuries long interseismic period (Wang et al . 2012 ). Several studies have revealed that the elastic Earth assumption tends to overestimate plate coupling in subduction zone setting as it ignores the effects introduced by viscous flow within the mantle wedge. Li et al . ( 2015 , 2018 ) conducted finite element modelling (FEM) to find that a purely elastic subduction zone model tends to overestimate the true coupling depth in North Chile and Cascadia. Li et al . ( 2020 ) showed that the assumption of a fully relaxed mantle may lead to underestimations of the coupling depth and/or plate coupling when ignoring the interseismic mantle relaxation. Furthermore, besides mantle viscoelasticity, simulations of post-seismic deformation following the 2013 Baluchistan earthquake show that the lower Makran accretionary wedge (12+ km depth) may undergo low-temperature viscoelastic deformation as well (Peterson et al . 2018 ; Cheng et al . 2022 ). Here, we conduct inversions of the GPS velocity data from Frohling & Szeliga ( 2016 ) for megathrust plate coupling of the MSZ using an FEM-derived Green's function under both elastic and viscoelastic Earth assumptions. We utilize the model resolution matrix derived from the Green's function to explore possible plate-coupling scenarios that the GPS observations could resolve. We then generate several megathrust earthquake scenarios based on these plate-coupling models and use them to forward model the corresponding tsunami responses at major coastal cities within the Persian Gulf, Arabian Sea and western Indian Ocean basin. The main goal of this study is to explore the population of subduction zone coupling scenarios, and by extension earthquake and tsunami scenarios, which are consistent with but incompletely resolved by the sparse geodetic observations currently available in the Makran.

2.1. Interseismic plate coupling: inversion and model resolution

Our analysis of coupling in the Makran focuses on modelling the resolution afforded by sparse campaign GPS measurements made prior to the 2013 M w 7.7 Baluchistan earthquake that occurred within the sub-aerial accretionary prism. We first use the fixed Eurasia GPS velocities from Frohling & Szeliga ( 2016 ) to invert for interseismic back-slip rate on the Makran megathrust. The back-slip model (Savage 1983 ) assumes that interseismic velocities or displacements reflect deformation due to coupling between two plates, such that the back-slip rate can be related to the magnitude of a slip deficit accrued on the plate interface that can later be released in an earthquake. Therefore, the slip deficit caused by fault coupling can be modelled as fault slip in the opposite sense to the coseismic slip (back-slip). The plate coupling is then defined as the ratio between back-slip rate during the modelled period, and the plate convergence rate at the trench. 11 out of 19 GPS stations from Frohling & Szeliga ( 2016 ) are used for the back-slip rate inversion (Fig.  1 ). The remaining eight stations lie either to the east or west of the MSZ where deformation is likely influenced by the strike-slip motion of the transverse fault systems. The GPS station coordinates and velocities were estimated using the GAMIT/GLOBK analysis package (Herring et al . 2010a , b ). Station coordinates and velocities were tied to the ITRF2008 global reference frame (Altamimi et al . 2011 ). The GPS velocities were rotated with respect to a fixed Eurasia reference frame using the pole-of-rotation parameters published in Altamimi et al . ( 2012 ).

We conduct the back-slip rate inversion based on a linear viscoelastic Makran accretionary prism model. The inverse problem describes the linear relationship between the back-slip rates on different fault patches and the surface displacement rates (i.e. GPS velocities) in the late stage of the interseismic period, when the post-seismic deformation from the previous large earthquake has diminished, and the surface deformation mainly results from interseismic megathrust loading. Thus, the inverse problem to solve for back-slip rate can be expressed as the linear system:

where G is the matrix of Green's functions relating unit back-slip rate on a fault patch at depth to velocities at a free surface, m is the unsolved back-slip rate vector and d is the data vector that contains the noisy GPS velocities. Following Barnhart & Lohman ( 2010 ), we apply least-squares inversion to solve for m , regularized by a minimum moment operator L , which minimizes slip on any given fault patch irrespective of the behaviour of adjacent patches. The regularized least-squares inversion minimizes the norm of

where L is an identity matrix, and λ is a weighting parameter that adjusts the degree to which the inversion is regularized. This regularization scheme is different from a spatial regularization scheme such as a Laplacian smoothing matrix. Therefore, the inverted slip distribution is not necessarily expected to be ‘smooth’ (i.e. constant spatial gradient between slip asperities). We compared the inversion results using minimum moment and Laplacian regularizations and found that due to the sparse distribution of the GPS stations, the Laplacian regularization introduces unrealistically high back-slip rate asperities downdip of the regional seismogenic zone ( Supporting Information Fig. S1 ). We explore the inversion results based on different λ values ( Supporting Information Fig. S2 ) and choose the best-fit λ value by identifying the corner of the L-curve (Harris & Segall 1987 ).

We construct the G matrix using FEM-derived Green's functions, following Masterlark ( 2003 ). We use the finite element meshing software Coreform-Cubit ( https://coreform.com/ ) to construct a layered viscoelastic 3-D subduction model, which is constrained by geophysical slab geometry (Craig & Copley 2014 ; Hayes et al . 2018 ), and material domains estimated from forward modelling of post-seismic deformation of the 2013 Baluchistan earthquake (Peterson et al . 2018 ; Cheng et al . 2022 ). The mesh geometry consists of four domains (Fig.  2 ): (1) an elastic upper wedge that extends to 12-km depth; (2) a Maxwell viscoelastic lower wedge that extends to a maximum depth of 40 km, which is the Moho depth reported in this region (Maggi et al . 2000 ; Shad Manaman et al . 2011 ; Abdollahi et al . 2018 ); (3) a 30 km thick elastic Arabian oceanic slab with megathrust geometry from the Slab2 model (Craig & Copley 2014 ; Hayes et al . 2018 ); and (4) a Maxwell viscoelastic oceanic and continental mantle at depths. To increase computational efficiency, instead of using the full megathrust mesh (10 350 patches in total), we discretize the plate interface into nonoverlapping patches with ∼30 km spacing (470 patches in total, Supporting Information Fig. S3 ). Each patch consists of sub-patches with a size on the scale of ∼15 km. We use open-source FEM software PyLith to assign material properties and derive the Green's functions (Aagaard et al . 2013 ). The materials properties for each domain are summarized in Supporting Information Table S1 . We set free displacement boundary condition at the ground surface. We fixed the displacements to be zero in the horizontal directions along the northern/southern boundaries and set the eastern/western boundaries to be free. We then prescribe unit back-slip rate (1 m yr −1 ) along strike and dip directions on one fault patch while keeping the slip rate zero on the remaining patches, and drive the simulation for 200 yr. The 200-yr simulation period is considerably longer than the Maxwell relaxation time of the viscoelastic materials (8 yr for the lower wedge, 50 yr for the mantle), which is an indication that the viscoelastic relaxation has stabilized and the simulation has reached the late stage of the interseismic period (Hu et al . 2004 ; Li et al . 2015 ). Additionally, we ignore any bias in the GPS velocity data that may be introduced by the prolonged post-seismic deformation of the 1945 Makran earthquake. For large (M > 8.5) subduction zone earthquakes, Li & Chen ( 2023 ) estimated the post-seismic phase to be in the range of 0.2–0.4 of their recurrence intervals. In the Makran region, the average recurrence time for magnitude 8 + earthquake is about 100–250 yr (Page et al . 1979 ). Therefore, although the post-seismic relaxation of the 1945 event may contribute to the GPS observations, we posit that this effect is small and the observed GPS velocities result solely from interseismic strain accumulation on the megathrust. We repeat the simulation process for every fault patch and calculate the surface velocities at the last time step, which are then flattened into column vectors and appended to the G matrix. For the elastic model, we calculate the G matrix following the same procedure as the viscoelastic model, but setting the material properties of the lower wedge and mantle domains to be elastic ( Supporting Information Table S1 ).

Makran subduction zone geometry and finite element mesh. Green domain: upper wedge. Blue domain: oceanic slab. Pink domain: lower wedge. Orange domain: oceanic and continental mantle.

After obtaining G , we solve for the back-slip rate vector m (eq.  3 ). We fix the rake to be 110°, a slip direction that both best explains the GPS observations based on a grid search procedure ( Supporting Information Fig. S4 ) and the relative plate motion resolved onto the subduction zone interface. We force the solution to be positive (slip along rake) and set the maximum allowable back-slip rate on each patch to be the plate convergence rate at the trench (fixed Eurasia reference frame, Altamimi et al . 2012 ). The regularized least squares solution can be written as

where m est is the estimated back-slip rate model. For each fault patch, we divide the interseismic back-slip rate model by the plate convergence rate at the trench to calculate the plate coupling. We translate the back-slip rate of each fault patch into the locking ratio by dividing the back-slip rate by the plate motion rate expected at the depth of each fault patch (Altamimi et al . 2012 ). We propagate the noise covariance structure of the data through the inversion and eq. ( 3 ) becomes:

where Ch is the inverse Cholesky factorization of the data covariance structure (Harris & Segall 1987 ).

2.2. Interseismic plate-coupling inversion: results

Fig.  3 shows the plate-coupling inversion results, as well as the model resolution matrices for elastic and viscoelastic models. The model resolution matrix ( R m ) is defined as

and reflects the degree of spatial averaging the inverted model has over the underlying true model (Menke 2018 ). To a first order, despite differences in the deeper part of the fault (below 20-km depth), both elastic and viscoelastic models exhibit similar magnitude and spatial distribution of plate coupling in the shallow portion (Figs  3a and  c ), which likely results from the lack of GPS data in the region to capture the viscoelastic effects. According to Li et al . ( 2015 , 2018 ), viscoelastic subduction zone behaviours affect interseismic deformation over longer spatial wavelength than simple elastic half-space models and thus dominate in the GPS signals further inland from the trench. Therefore, the lack of GPS stations in inland Makran may cause the inversion results from the viscoelastic model to be indistinguishable from the elastic model.

Inverted interseismic plate-coupling models and the diagonal components of the model resolution matrices of the Makran megathrust resulting from (a and b) viscoelastic model and (c and d) elastic model. (e) L-curve between the fit to data (data norm) and the model size (model norm), and the selected corner ( λ ) for each coupling model. White arrows: GPS velocity data from Frohling & Szeliga ( 2016 ); pink arrows: forward-predicted velocities from the inversion; black solid lines: contours of the plate interface marked by depth in kilometer; black dash lines: boundaries between different fault segments; dark green lines: coastlines.

For both models, five regions with relatively high magnitudes of coupling are observed along strike at about 10-km depth. These coupled patches correspond to high values in the model resolution matrix (Figs  3b and  d ), indicating that the plate coupling is high where coupling is well-resolved by the data. We observe along-strike variation in the coupling ratio over these five regions. The westernmost and two easternmost regions exhibit higher coupling with respect to the two central regions, indicating likely segmentation of the Makran megathrust with varying coupling from west to east (Fig.  3 ). This pattern is consistent with previous coupling estimates of the MSZ that suggested that the western and eastern segments have higher coupling (∼58 per cent), while the central segment is weakly coupled (∼31 per cent, Frohling & Szeliga 2016 ). Distributed high coupling extends below 20-km depth in our model. However, we find these estimates to likely be an artifact of the distribution of surface observations given that the model resolution matrix exhibits low values over the corresponding fault areas. Moreover, historic reviews of Makran seismicity suggest that, with the exception of intermediate depth normal faulting earthquakes, nearly all recorded earthquakes occur at depths shallower than 20 km (Jackson & McKenzie 1984 ; Byrne et al . 1992 ), further suggesting that this downdip ‘smear’ of high coupling is likely unreal, but rather an artifact resulting from the lack of GPS observations in the vicinity of the fault areas.

3.1. Model resolution

After undertaking inversions of the GPS observations for back slip rates, we explore the potential characteristics of back slip that cannot be resolved by the sparsely located geodetic measurements. An inverse model ( m est ) of back-slip rate (or fault slip, more generally) only reveals what aspects of the true, underlying back-slip rate distribution ( m true ) can be resolved given the location and quality of data, the imposed fault model (location, discretization), the imposed Earth structure, inversion regularization, and other sources of epistemic uncertainty. The resolution capabilities of an inverse problem need to be assessed in order to characterize the full range of potential underlying, true scenarios. Model resolution matrix ( R m ) gives what a true model looks like with the available data collection strategy.

We use the model resolution matrix to interrogate this relationship between our inverted back-slip rate distributions ( m est ) and the unknown true back-slip rate distribution ( m true ) in order to define a suite of possible true back-slip rate distributions. The relationship between the true underlying back-slip rate model ( m true ) and the inverted, estimated back-slip rate model ( m est ) is

Using eq. ( 6 ) and our inverted back-slip rate model ( m est ), we can then multiply any conjured, theoretical coupling scenario by the model resolution matrix, and then compare the output to our inverted coupling models and determine if the theoretical coupling scenario is possible given the model resolution. Fig.  4 illustrate the relationship between R m , m est and m true .

A general illustration of relationship between true back-slip rate ( m true ), model resolution matrix ( R m ) and inverted back-slip rate ( m est ) in back-slip rate inversion on a subduction interface. The model resolution matrix in this figure is constructed based on synthetic GPS velocities that are equally spaced on both land and seafloor.

To construct different scenarios of m true , we first divide the megathrust into three segments as previously described by varying coupling ratio (Fig.  3 ). We create in total of six back-slip rate scenarios on either one or multiple segments: east-only (E), central-only (C), west-only (W), east-central (EC), west-central (WC), and whole-fault (WCE). For each scenario, we assume that the interseismic back-slip rate extends to the trench and assign a series of combinations of downdip width and back-slip rate ( m true ). Since there is little information on the downdip limit of plate coupling, and the model resolution is low at depth (Fig.  3 ), we keep the downdip widths as narrow as possible. Therefore, the downdip widths estimated in this study reflect the shallowest plate-coupling limits that can be constrained by the GPS data. We then multiply m true by the R m from our viscoelastic inversion to calculate how the back-slip rate distribution would be resolved after the inversion ( m rsv ). In a trial-and-error manner, we calculate the root-mean-square error (RMSE) between m rsv and the inversion result m est to access whether the prescribed back-slip rate scenarios, under given model resolution, can produce the same back-slip rate pattern as the GPS inversion. Additionally, we conduct visual inspections to assess the fit between m rsv and m est within the ruptured segment(s) to ensure that actual back-slip rates are being fit, rather than noises (i.e. the downdip artifact shown in Fig.  3 ).

After obtaining different scenarios of m true , we divide them by the plate convergence rate at the trench to calculate the corresponding plate-coupling models. For each scenario, we use an earthquake scaling relationship to estimate an earthquake moment magnitude. This moment magnitude corresponds to a possible future earthquake where the entire coupled segment(s) is ruptured. We use the scaling relationship between fault area and magnitude described in Allen & Hayes ( 2017 ), which is developed based on earthquakes in subduction zone and offshore environments:

where M w is the moment magnitude, FA is fault area in square kilometres, and a and b are regression coefficients that are set to be −3.63 and 0.96, respectively. After solving for the seismic moment magnitude, we calculate the coseismic uniform slip magnitude following

where m o is the seismic moment release, D is the uniform fault slip, A is the summation of areas of all fault patches above the downdip limit and μ is shear modulus fixed at 40 GPa.

We further investigate scenarios where interseismic back-slip rate does not extend to the trench, but starts at certain depth downdip. To do this, for each scenario, we test combinations of back-slip rate and upper coupling depth limit while keeping the lower limit the same as before, and look for the best-fitting back-slip rate case, whose corresponding plate-coupling model and future earthquake slip magnitude are calculated following the same procedure as before.

3.2. Coupling-based earthquake scenarios: results

Figs  5 and  6 show the best-fitting plate-coupling models for all six back-slip rate scenarios under trench slip and blind slip conditions, respectively. Supporting Information Table S2 summarizes the source parameters for each back-slip rate scenario and the corresponding future earthquake. We observe several characteristics for different plate-coupling cases. In general, back-slip rate scenarios where locking extends to the trench produce trench-rupturing earthquakes of higher magnitudes than their blind-rupturing counterparts. For example, if the interseismic strain accumulation is released through an earthquake on the east-central segments, the magnitude of the earthquake is 9.0 and 8.7, under trench rupture and blind rupture conditions, respectively. We observe that single-segment coupling models, after being multiplied by the model resolution matrix, yield better fits to the GPS-inverted coupling model than the multisegment models within the corresponding segments. For instance, the east-only coupling model shows lower residuals than the whole-fault case within the eastern segment. Single-segment ruptures also produce lower magnitude than multisegment ruptures. Our results suggest that the Makran megathrust may be able to produce earthquakes up to M w 8.7 for single-segment rupture, and M w 9.2 for multisegment rupture. Additionally, the plate-coupling distributions for the east-only, central-only, and west-only back-slip rate cases indicate higher coupling in the eastern (50–60 per cent) and western (60–70 per cent) segments than the central segment (30–35 per cent, Fig.  7 ), which is again consistent with the results from Frohling & Szeliga ( 2016 ). Finally, when comparing the misfit between the GPS data and the forward-predicted velocities, we find that the prescribed back-slip scenarios yield good fit to data at stations close to the coupled patches. However, the westmost station exhibit large misfit exceeding the GPS uncertainty. This could result either from the spatially variable coupling on the western section or bias in the GPS velocity associated with the right-lateral motion on the nearby Minab–Zendan fault system.

Best-fitting single- and multisegment plate-coupling scenarios and the corresponding earthquake magnitudes under the trench slip condition. The first column shows the assigned plate coupling corresponding to each back-slip rate case. The second column shows the resolvable coupling (multiply the first column by the corresponding model resolution matrix). The third column shows the residual between the resolvable coupling and the inverted coupling shown in Fig.  3 . Each moment magnitude corresponds to an earthquake for the given coupling scenario assuming that the interseismic strain accumulation is fully released. White and pink arrows in the first column correspond to GPS velocity data and forward-predicted velocities, respectively.

Best-fitting single- and multisegment plate-coupling scenarios and the corresponding earthquake magnitudes under the blind slip condition.

The preferred coupling model of the Makran megathrust and its resolvability by the GPS data.

4.1. Tsunami simulations in the western Indian Ocean: methods

For each earthquake slip scenario, we calculate co-seismic ground/seafloor vertical displacements using Pylith . We use the same subduction zone geometry as before with the lower wedge exhibiting Maxwell rheology. We prescribe the slip distributions onto the megathrust and simulate the co-seismic surface static vertical displacements. Supporting Information Fig. S5 shows the resulting ground/seafloor uplift patterns. We then input these surface vertical displacements as initial condition for tsunami simulations using the open-source tsunami modelling code GeoClaw ( http://www.clawpack.org/geoclaw ). We ignore the time-dependent co-seismic slip evolution and assume that the earthquakes instantly deform the seafloor, as earthquake rupture propagates much faster than tsunami wave. We use the SRTM15 + relief model resampled at 1-arcminute pixel resolution for both topography and bathymetry inputs (Tozer et al . 2019 ). GeoClaw solves 2-D shallow water equations with finite volume technique (LeVeque et al . 2011 ), and employs adaptive mesh refinement (AMR) which automatically refines regions of higher tsunami complexity to finer mesh size according to user inputs. We use two levels of grid refinement with the coarsest set at 2-arcminute and the finest at 1-arcminute for the topography/bathymetry data set. For each earthquake scenario, we drive the tsunami simulation for 12 hours following the rupture. We then output time-series of estimated tsunami amplitudes (ETA) at 20 virtual tide gauges outside major port cities along coastlines bounding the Oman sea, the Strait of Hormuz, and southwestern Indian Ocean basin. Since the gauge points are located at different water depths, we apply Green's law to rescale the ETA to a common reference depth of 1 m following (Small & Melgar 2021 ).

4.2. Tsunami simulations in the western Indian Ocean: results

Fig.  8 illustrates the maximum tsunami wave heights calculated at the 20 tide gauge points for all six rupture scenarios under trench rupture and blind rupture conditions, respectively. Supporting Information Tables S3 and S4 summarize the maximum and peak-to-peak tsunami wave height results. In general, we observe spatial variation in the maximum and peak-to-peak tsunami wave heights in different regions of the western Indian Ocean basin. Fig.  9 shows the modelled ETA time-series resulting from the M w 9.2 whole-fault trench-rupturing earthquake, and Fig.  10 shows the corresponding tsunami snapshots. We group the gauge points into four spatial domains with variable maximum wave height ranges: the northern Arabian Sea region, the west coast of India, eastern Africa, and the Strait of Hormuz. Following the M w 9.2 rupture, coastal cities in the northern Arabian Sea region, including Muscat, Chah Bahar, Gwadar, Pasni, and Ormara, and Karachi, experience the most tsunami hazard with the maximum wave height reaching 2-5 m and peak-to-peak wave height reaching 4-9 m ( Supporting Information Tables S3 and S4 ). Cities on the west coast of India (i.e. Surat, Mumbai, Mangalore, Kozhikode, and Kochi) are less affected, with wave height reaching 1–1.5 m (peak-to-peak: 1-3 m). Coastal cities bounding eastern Africa (i.e. Mogadishu, Dar es Salaam, Maputo, and Durban), and the Strait of Hormuz (i.e. Kuwait City, Dammam, Doha, Abu Dhabi, Dubai), are the least affected, with the incoming maximum and peak-to-peak wave height less than 1 m.

Maximum tsunami wave heights at 20 synthetic gauge points (cyan circles) following single- and multisegment trench rupturing (red) and blind (green) earthquakes.

Modelled tsunami wave height time-series at gauge points offshore major coastal cities in the western Indian Ocean region following the M w 9.2 whole-fault trench-rupturing earthquake.

Modelled tsunami wave propagation after the M w 9.2 whole-fault trench-rupturing earthquake. Solid circles indicate gauge point locations offshore major coastal cities.

5.1. Seismic potential of the Makran megathrust

Our preferred plate-coupling model (Fig.  7 ) suggests that coupling varies along the strike of the subduction zone. We divide the MSZ into three regions based on the average coupling ratio, which are spatially similar to the three segments defined by Frohling & Szeliga ( 2016 ). The eastern segment, spanning from west of Pasni, Pakistan (63.2°E) to the eastern end of the domain (66.2°E), exhibits approximately 50 per cent coupling. This region hosted the 1945 M w 8.0–8.3 megathrust earthquake (Byrne et al . 1992 ). The central segment spans from west of Chah Bahar, Iran (60°E) to the west of Pasni (63.2°E) and shows a reduced plate coupling of ∼30 per cent. Historically, this section of the fault has experienced few major earthquakes, with only two coastal events recorded in 1851 and 1864 (Fig.  1 ). Lastly, the western segment, from west of Chah Bahar (60°E) to the western end of the domain (57.2°E), is approximately 60 per cent coupled. However, the coupling of this segment is not well-resolved when compared to the other two segments, as the back-slip rate inversion is noisy downdip of the regional seismogenic zone. This likely results from low GPS station coverage in the region, or neglecting the stress partitioning contributed by the Minab–Zendan fault system to the west.

Segmentation of the megathrust implies variation in degree of earthquake hazard potential along the MSZ. Following the asperity model of Lay & Kanamori ( 1981 ), strong plate coupling corresponds to larger asperity size and is more likely to produce larger events, whereas weak coupling indicates smaller asperity size and likely results in smaller events. Higher plate coupling is also an indication of faster interseismic strain accumulation on the megathrust, where subduction zone earthquakes yield shorter recurrence intervals than those of the same magnitudes but produced on weakly coupled plate interfaces. We calculate the recurrence intervals for all earthquake scenarios by dividing the uniform co-seismic slip magnitudes by the back-slip rates ( Supporting Information Table S2 ). The results show that, under trench-rupture condition, the recurrence intervals for an M w 8.7 earthquake that ruptures the eastern, central and western segments are approximately 373, 664 and 381 yr, respectively, with unknown uncertainties. This change in recurrence interval correlates to the variation in plate coupling from east to west, where the eastern and western segments are stronger coupled than the central segment, resulting in shorter recurrence intervals for earthquakes of a given magnitude. Therefore, the eastern and western Makran are likely able to host larger, more frequent earthquake events than the central Makran.

5.2. Tsunami hazard potential in the western Indian Ocean basin

Our coupling-based tsunami simulation indicates variations in expected tsunami wave height along the coastline bounding the western Indian Ocean basin. In the largest earthquake scenario where the entire megathrust is rupture to the trench, the northern Arabian Sea region experiences the most severe tsunami hazard with the maximum wave height reaching several coastal cities at 2–5 m within the first hour after the earthquake ( Supporting Information Table S3 , Figs  9 and  10 ). The peak tsunami wave reduces to 1–1.5 m height and arrives at the west coast of India after 4 hr. The east coast of Africa and the Strait of Hormuz are the least affected by the M w 9.2 earthquake in Makran, where the incoming maximum wave height is less than 1 m. For all 20 virtual gauge points, we define and calculate a simple index, termed the tsunami hazard score (THS), to assess the tsunami hazard potential at each location considering all 12 possible earthquake scenarios in Makran. The THS is defined as the weighted sum of number of events exceeding given maximum tsunami wave height thresholds at a gauge point for all 12 earthquake events, normalized between 0 and 100:

where N i is the number of events producing maximum wave height larger than W i metres (from 1 to 4.5 m, 0.5-m increment). Supporting Information Table S5 shows the THS summary for all 20 coastal cities. Again, cities in the northern Arabian Sea region yield the highest THS (i.e. having the highest tsunami potential from earthquakes in Makran). Coastal cities in western India yield lower THS values, and cities in eastern Africa and the Strait of Hormuz have the lowest score. Specifically, Muscat, Char Bhar and Gwadar are the three cities with highest THS values. Muscat is the capital and the most populated city in Oman. Char Bhar and Gwadar are the two of the fastest-growing commercial port cities in the region. Tsunami events of maximum wave height of 3–5 m at these locations can cause severe destruction to coastal infrastructures and port facilities, and result in significant human casualties and economic losses.

Tsunami height records and observations in the Makran are incomplete. The 1945 M w 8.0–8.3 earthquake is the first instrumentally recorded event, and the only event for which observations of tsunami wave heights along different coasts are available (Heidarzadeh et al . 2008 ). According to Berninghausen ( 1966 ), the wave heights were at about 12–15 m at Pasni and Ormara, and 1.4 m at Karachi. Ambraseys & Melville ( 2005 ) reported the wave height to be about 4–5 m in Pasni and 1.5 m in Karachi. Adams et al . ( 2018 ) detided a Karachi tide-gauge record and reported the water level to be ∼0.5 m above ambient tide. Page et al . ( 1979 ) reported a wave height reaching 7–10 m along several parts of the Makran coast. Since the 1945 earthquake ruptured in the eastern segment of the megathrust, we compare our predicted maximum tsunami wave heights from the east-only trench-rupture scenario to the field observations. Our model suggests a maximum wave height of 1.28 m in Karachi, which is in reasonable agreement with the field observations. However, the wave height predictions at Pasni and Ormara are much lower (1.15 and 1.32 m, respectively) than the 12–15 m reported by previous studies. This discrepancy between modelling results and field observations is consistent with other numerical models of this earthquake (Heidarzadeh et al . 2008 ; Heidarzadeh & Satake 2015 ; Qiu et al . 2022 ). Heidarzadeh et al . ( 2008 ) proposed three possible explanations for this discrepancy: (1) the reports of 12–15 m wave heights were incorrect and an exaggeration; (2) the large wave heights resulted from submarine landslides triggered by the earthquake; and (3) the elevated wave heights could be produced by large displacements on splay faults near the trench, which are not considered in our models. Qiu et al . ( 2022 ) conducted tsunami simulations of the 1945 megathrust rupture with additional displacements on splay faults. Their results indicate amplification of tsunami wave height when considering the presence of splay faults.

Although we cannot currently resolve megathrust coupling in the MSZ with the resolution that can be accomplished in other global subduction zones, this study serves to provide a synopsis of what is possible given our current data availability. By developing coupling scenarios that are consistent with the model resolution of our inverse problem, we are able to hypothesize several important characteristics of coupling in the MSZ and how future great earthquakes may play out:

The plate-coupling distribution that can be directly inferred from available GPS observations is insufficient to uniquely explain the history of great earthquakes in the Makran; thus, there is significant coupling that cannot be directly resolved with current observations.

The megathrust of the MSZ is likely segmented with variable plate coupling along strike, in agreement with previous studies. The eastern and western segments correspond to approximately 50 and 60 per cent coupling, respectively. The central segment exhibits lower coupling (about 30 per cent) than the other two segments.

Our investigation suggests that, based on the inverted plate coupling, the Makran megathrust may be able to produce earthquakes up to M w 8.7 for single-segment rupture, and M w 9.2 for multisegment rupture.

Population centres along the western Indian Ocean basin may be exposed to tsunami hazard as a result of Makran great earthquakes. The northern Arabian Sea region experiences the most severe tsunami hazard with the maximum wave height reaching several coastal cities at 2–5 m. The west coast of India is less affected with wave height reduced to 1–1.5 m. The east coast of Africa and the Strait of Hormuz are the least affected, for which the incoming wave height is less than 1 m.

This work was supported by NSF Award EAR 1917500. High-performance computational resources were provided by the University of Iowa, Iowa City. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

The GPS velocity data used to invert for interseismic plate coupling were imported from Frohling & Szeliga ( 2016 ). Several figures were generated using the Generic Mapping Tool (Wessel et al . 2013 ).

Aagaard B.T. , Knepley M.G. , Williams C.A. 2013 . A domain decomposition approach to implementing fault slip in finite-element models of quasi-static and dynamic crustal deformation . J. geophys. Res. , 118 ( 6 ), 3059 – 3079 . 10.1002/jgrb.50217

Google Scholar

Abdollahi S. , Ardestani V.E. , Zeyen H. , Shomali Z.H. 2018 . Crustal and upper mantle structures of Makran subduction zone, SE Iran by combined surface wave velocity analysis and gravity modeling . Tectonophysics , 747–748 , 191 – 210 . 10.1016/j.tecto.2018.10.005

Adams L.M. , Atwater B.F. , Hasan H. 2018 . Karachi tides during the 1945 Makran tsunami . Geosci. Lett. , 5 ( 1 ), 25 . doi: 10.1186/s40562-018-0121-z . 10.1186/s40562-018-0121-z

Allen T.I. , Hayes G.P. 2017 . Alternative rupture-scaling relationships for subduction interface and other offshore environments . Bull. seism. Soc. Am. , 107 ( 3 ), 1240 – 1253 . 10.1785/0120160255

Altamimi Z. , Collilieux X. , Métivier L. 2011 . ITRF2008: an improved solution of the international terrestrial reference frame . J. Geod. , 85 ( 8 ), 457 – 473 . 10.1007/s00190-011-0444-4

Altamimi Z. , Métivier L. , Collilieux X. 2012 . ITRF2008 plate motion model . J. geophys. Res. , 117 ( B7 ). doi: 10.1029/2011JB008930 . 10.1029/2011JB008930

Ambraseys N.N. , Melville C.P. 2005 . A History of Persian Earthquakes . Cambridge Univ. Press .

Google Preview

Baptista M.A. , Miranda J.M. , Omira R. , El Hussain I. 2020 . Study of the 24 September 2013 Oman Sea tsunami using linear shallow water inversion . Arabian Journal of Geosciences , 13 ( 14 ), 606 . doi: 10.1007/s12517-020-05632-z . 10.1007/s12517-020-05632-z

Barnhart W.D. , Hayes G.P. , Samsonov S.V. , Fielding E.J. , Seidman L.E. 2014 . Breaking the oceanic lithosphere of a subducting slab: the 2013 Khash, Iran earthquake . Geophys. Res. Lett. , 41 ( 1 ), 32 – 36 . 10.1002/2013GL058096

Barnhart W.D. , Lohman R.B. 2010 . Automated fault model discretization for inversions for coseismic slip distributions . J. geophys. Res. , 115 ( B10 ). doi: 10.1029/2010JB007545 . 10.1029/2010JB007545

Berninghausen W..H. 1966 . Tsunamis and seismic seiches reported from regions adjacent to the Indian Ocean . Bull. seism. Soc. Am. , 56 ( 1 ), 69 – 74 . 10.1785/BSSA0560010069

Burg J.-P. 2018 . Geology of the onshore Makran accretionary wedge: synthesis and tectonic interpretation . Earth Sci. Rev. , 185 , 1210 – 1231 . 10.1016/j.earscirev.2018.09.011

Byrne D.E. , Sykes L.R. , Davis D.M. 1992 . Great thrust earthquakes and aseismic slip along the plate boundary of the Makran Subduction Zone . J. geophys. Res. , 97 ( B1 ), 449 – 478 . 10.1029/91JB02165

Cheng G. , Barnhart W.D. , Li S. 2022 . Power-law viscoelastic flow of the lower accretionary prism in the Makran subduction zone following the 2013 Baluchistan earthquake . J. geophys. Res. , 127 ( 11 ), e2022JB024493 . doi: 10.1029/2022JB024493 . 10.1029/2022JB024493

Craig T.J. , Copley A. 2014 . An explanation for the age independence of oceanic elastic thickness estimates from flexural profiles at subduction zones, and implications for continental rheology . Earth planet. Sci. Lett. , 392 , 207 – 216 . 10.1016/j.epsl.2014.02.027

DeMets C. , Gordon R.G. , Argus D.F. 2010 . Geologically current plate motions . Geophys. J. Int. , 181 ( 1 ), 1 – 80 . 10.1111/j.1365-246X.2009.04491.x

Fowler S.R. , White R.S. , Louden K.E. 1985 . Sediment dewatering in the Makran accretionary prism . Earth planet. Sci. Lett. , 75 ( 4 ), 427 – 438 . 10.1016/0012-821X(85)90186-4

Frohling E. , Szeliga W. 2016 . GPS constraints on interplate locking within the Makran subduction zone . Geophys. J. Int. , 205 ( 1 ), 67 – 76 . 10.1093/gji/ggw001

Harris R.A. , Segall P. 1987 . Detection of a locked zone at depth on the Parkfield, California, segment of the San Andreas Fault . J. geophys. Res. , 92 ( B8 ), 7945 – 7962 . 10.1029/JB092iB08p07945

Hayes G.P. , Moore G.L. , Portner D.E. , Hearne M. , Flamme H. , Furtney M. , Smoczyk G.M. 2018 . Slab2, a comprehensive subduction zone geometry model . Science , 362 ( 6410 ), 58 – 61 . 10.1126/science.aat4723

Heck N.H. 1947 . List of seismic sea waves* . Bull. seism. Soc. Am. , 37 ( 4 ), 269 – 286 . 10.1785/BSSA0370040269

Heidarzadeh M. , Pirooz M.D. , Zaker N.H. , Yalciner A.C. , Mokhtari M. , Esmaeily A. 2008 . Historical tsunami in the Makran subduction zone off the southern coasts of Iran and Pakistan and results of numerical modeling . Ocean Eng. , 35 ( 8 ), 774 – 786 . 10.1016/j.oceaneng.2008.01.017

Heidarzadeh M. , Satake K. 2015 . New insights into the source of the Makran tsunami of 27 November 1945 from tsunami waveforms and coastal deformation data . Pure appl. Geophys. , 172 ( 3 ), 621 – 640 . 10.1007/s00024-014-0948-y

Herring T.A. , King R.W. , McClusky S.C. 2010a . GAMIT reference manual, GPS analysis at MIT release 10.4 . Tech. Rep., Dept. Earth Atmos. Planet. Sci. Mass. Inst. Technol., Cambridge, MA .

Herring T.A. , King R.W. , McClusky S.C. 2010b . GLOBK: global Kalman filter VLBI and GPS analysis program, release 10.4 . Tech. Rep., Dept. Earth Atmos. Planet. Sci. Mass. Inst. Technol., Cambridge, MA .

Hoffmann G. , Grützner C. , Reicherter K. , Preusser F. 2015 . Geo-archaeological evidence for a Holocene extreme flooding event within the Arabian Sea (Ras al Hadd, Oman) . Quat. Sci. Rev. , 113 , 123 – 133 . 10.1016/j.quascirev.2014.09.033

Hu Y. , Wang K. , He J. , Klotz J. , Khazaradze G. 2004 . Three-dimensional viscoelastic finite element model for postseismic deformation of the great 1960 Chile earthquake . J. geophys. Res. , 109 ( B12 ). doi: 10.1029/2004JB003163 . 10.1029/2004JB003163

Jackson J. , McKenzie D. 1984 . Active tectonics of the Alpine–Himalayan Belt between western Turkey and Pakistan . Geophys. J. R. Astron. Soc. , 77 ( 1 ), 185 – 264 . 10.1111/j.1365-246X.1984.tb01931.x

Kopp C. , Fruehn J. , Flueh E.R. , Reichert C. , Kukowski N. , Bialas J. , Klaeschen D. 2000 . Structure of the Makran subduction zone from wide-angle and reflection seismic data . Tectonophysics , 329 ( 1 ), 171 – 191 . 10.1016/S0040-1951(00)00195-5

Lay T. , Kanamori H. 1981 . An asperity model of large earthquake sequences , in Earthquake Prediction , pp. 579 – 592 ., American Geophysical Union (AGU) . doi: 10.1029/ME004p0579 . 10.1029/ME004p0579

LeVeque R.J. , George D.L. , Berger M.J. 2011 . Tsunami modelling with adaptively refined finite volume methods* . Acta Numer. , 20 , 211 – 289 . 10.1017/S0962492911000043

Li S. , Chen L. 2023 . How long can the postseismic and interseismic phases of great subduction earthquake sustain? Toward an integrated earthquake-cycle perspective . Geophys. Res. Lett. , 50 ( 11 ), e2023GL103976 . doi: 10.1029/2023GL103976 . 10.1029/2023GL103976

Li S. , Fukuda J. , Oncken O. 2020 . Geodetic evidence of time-dependent viscoelastic interseismic deformation driven by megathrust locking in the southwest Japan subduction zone . Geophys. Res. Lett. , 47 ( 4 ), e2019GL085551 . doi: 10.1029/2019GL085551 . 10.1029/2019GL085551

Li S. , Moreno M. , Bedford J. , Rosenau M. , Oncken O. 2015 . Revisiting viscoelastic effects on interseismic deformation and locking degree: a case study of the Peru–North Chile subduction zone . J. geophys. Res. , 120 ( 6 ), 4522 – 4538 . 10.1002/2015JB011903

Li S. , Wang K. , Wang Y. , Jiang Y. , Dosso S.E. 2018 . Geodetically inferred locking state of the Cascadia megathrust based on a viscoelastic earth model . J. geophys. Res. , 123 ( 9 ), 8056 – 8072 . 10.1029/2018JB015620

Lin Y.N. , Jolivet R. , Simons M. , Agram P.S. , Martens H.R. , Li Z. , Lodi S.H. 2015 . High interseismic coupling in the Eastern Makran (Pakistan) subduction zone . Earth planet. Sci. Lett. , 420 , 116 – 126 . 10.1016/j.epsl.2015.03.037

Maggi A. , Jackson J.A. , Priestley K. , Baker C. 2000 . A re-assessment of focal depth distributions in southern Iran, the Tien Shan and northern India: do earthquakes really occur in the continental mantle? . Geophys. J. Int. , 143 ( 3 ), 629 – 661 . 10.1046/j.1365-246X.2000.00254.x

Masterlark T. 2003 . Finite element model predictions of static deformation from dislocation sources in a subduction zone: sensitivities to homogeneous, isotropic, Poisson-solid, and half-space assumptions . J. geophys. Res. , 108 ( B11 ). doi: 10.1029/2002JB002296 . 10.1029/2002JB002296

Menke W. 2018 . Geophysical Data Analysis: Discrete Inverse Theory . Academic Press .

Mokhtari M. , Ala Amjadi A. , Mahshadnia L. , Rafizadeh M. 2019 . A review of the seismotectonics of the Makran subduction zone as a baseline for tsunami hazard assessments . Geosci. Lett. , 6 ( 1 ), 13 . doi: 10.1186/s40562-019-0143-1 . 10.1186/s40562-019-0143-1

Musson R.M.W. 2009 . Subduction in the Western Makran: the historian's contribution . J. Geol. Soc. , 166 ( 3 ), 387 – 391 . 10.1144/0016-76492008-119

Okada Y. 1992 . Internal deformation due to shear and tensile faults in a half-space . Bull. seism. Soc. Am. , 82 ( 2 ), 1018 – 1040 . 10.1785/BSSA0820021018

Page W.D. , Alt J.N. , Cluff L.S. , Plafker G. 1979 . Evidence for the recurrence of large-magnitude earthquakes along the Makran coast of Iran and Pakistan . Tectonophysics , 52 ( 1 ), 533 – 547 . 10.1016/0040-1951(79)90269-5

Peterson K.E. , Barnhart W.D. , Li S. 2018 . Viscous accretionary prisms: viscoelastic relaxation of the Makran accretionary prism following the . 2013 Baluchistan, Pakistan earthquake . J. geophys. Res. , 123 ( 11 ), 10 107 – 10 123 . 10.1029/2018JB016057

Platt J.P. , Leggett J.K. , Young J. , Raza H. , Alam S. 1985 . Large-scale sediment underplating in the Makran accretionary prism, southwest Pakistan . Geology , 13 ( 7 ), 507 – 511 . 10.1130/0091-7613(1985)13<507:LSUITM>2.0.CO;2

Qiu Q. , Zhou Z. , Lin J. , Zhang F. , Chen Z. , Yang X. 2022 . Great earthquake and tsunami potential in the eastern Makran subduction zone: new insights from geodetic and structural constraints . Tectonophysics , 837 , 229462 . 10.1016/j.tecto.2022.229462

Quittmeyer R.C. , Jacob K.H. 1979 . Historical and modern seismicity of Pakistan, Afghanistan, northwestern India, and southeastern Iran . Bull. seism. Soc. Am. , 69 ( 3 ), 773 – 823 . 10.1785/BSSA0690030773

Rajendran C.P. , Rajendran K. , Shah-hosseini M. , Beni A.N. , Nautiyal C.M. , Andrews R. 2013 . The hazard potential of the western segment of the Makran subduction zone, northern Arabian Sea . Nat. Hazards , 65 ( 1 ), 219 – 239 . 10.1007/s11069-012-0355-6

Regard V. et al.  2010 . The transition between Makran subduction and the Zagros collision: recent advances in its structure and active deformation . Geol. Soc. London Spec. Publ. , 330 ( 1 ), 43 – 64 .

Savage J.C. 1983 . A dislocation model of strain accumulation and release at a subduction zone . J. geophys. Res. , 88 ( B6 ), 4984 – 4996 . 10.1029/JB088iB06p04984

Shad Manaman N. , Shomali H. , Koyi H. 2011 . New constraints on upper-mantle S-velocity structure and crustal thickness of the Iranian plateau using partitioned waveform inversion . Geophys. J. Int. , 184 ( 1 ), 247 – 267 . 10.1111/j.1365-246X.2010.04822.x

Small D.T. , Melgar D. 2021 . Geodetic coupling models as constraints on stochastic earthquake ruptures: an example application to PTHA in Cascadia . J. geophys. Res. , 126 ( 7 ), e2020JB021149 . doi: 10.1029/2020JB021149 . 10.1029/2020JB021149

Smith G. , McNeill L. , Henstock T.J. , Bull J. 2012 . The structure and fault activity of the Makran accretionary prism . J. geophys. Res. , 117 ( B7 ). doi: 10.1029/2012JB009312 . 10.1029/2012JB009312

Tozer B. , Sandwell D.T. , Smith W.H.F. , Olson C. , Beale J.R. , Wessel P. 2019 . Global bathymetry and topography at 15 arc sec: SRTM15+ . Earth Space Sci. , 6 ( 10 ), 1847 – 1864 . 10.1029/2019EA000658

Wang K. , Hu Y. , He J. 2012 . Deformation cycles of subduction earthquakes in a viscoelastic Earth . Nature , 484 , 327 – 332 . 10.1038/nature11032

Wessel P. , Smith W.H.F. , Scharroo R. , Luis J. , Wobbe F. 2013 . Generic Mapping Tools: improved version released . EOS, Trans. Am. geophys. Un. , 94 ( 45 ), 409 – 410 . 10.1002/2013EO450001

Supplementary data

Fig. S1 . Inverted plate-coupling models using (a) minimum moment and (b) Laplacian regularization.

Fig. S2 . Inverted interseismic viscoelastic plate-coupling models of the Makran megathrust and the diagonal components of the model resolution matrices using varying smoothing coefficient. White arrows: GPS velocity data; Pink arrows: forward-predicted velocity from the inversion; Black solid lines: contours of the plate interface marked by depth in kilometer; Black dash lines: boundaries between different fault segments. Dark green lines: coastlines.

Fig. S3 . Example of 3 nonoverlapping fault patches for inversion approach. When calculating the surface deformation resulting from slipping of each patch, we apply unit slip to the nodes located in the patch of interest while applying zero slip to all the other nodes on the fault.

Fig. S4 . Misfit between the observed and predicted GPS velocities using different rake values in the back-slip rate inversion.

Fig. S5 . Co-seismic static ground/seafloor vertical displacements resulting from single- and multi-segment earthquakes under both trench rupture and blind rupture conditions.

Table S1 . Four model domains and their material properties used in the generation of Green’s functions for both elastic and viscoelastic models.

Table S2 . Source parameters for all back-slip scenarios and the corresponding future earthquake cases.

Table S3 . Maximum tsunami wave height response (in meters) at the 20 tide gauge points (cities) resulting from 12 rupture scenarios under both trench rupture and blind rupture conditions.

Table S4 . Peak-to-peak tsunami wave height response (in meters) at the 20 tide gauge points (cities) resulting from 12 rupture scenarios under both trench rupture and blind rupture conditions.

Table S5 . Occurrence of events larger than certain maximum wave height thresholds and Tsunami Hazard Score (THS) at the 20 tide gauge points (cities).

Email alerts

Astrophysics data system, citing articles via.

• Recommend to your Library
• Advertising and Corporate Services
• Journals Career Network

Affiliations

• Online ISSN 1365-246X
• Print ISSN 0956-540X
• Copyright © 2024 The Royal Astronomical Society
• About Oxford Academic
• Publish journals with us
• University press partners
• What we publish
• New features  
• Open access
• Institutional account management
• Rights and permissions
• Get help with access
• Accessibility
• Advertising
• Media enquiries
• Oxford University Press
• Oxford Languages
• University of Oxford

Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide

• Copyright © 2024 Oxford University Press
• Cookie settings
• Cookie policy
• Privacy policy
• Legal notice

This Feature Is Available To Subscribers Only

Sign In or Create an Account

This PDF is available to Subscribers Only

For full access to this pdf, sign in to an existing account, or purchase an annual subscription.

USS Ronald Reagan leaves its Japan home port after nearly 9 years

• Show more sharing options
• Copy Link URL Copied!

A U.S. Navy strike group’s flagship aircraft carrier left its Japanese home port on Thursday, wrapping up nearly nine years of deployment in the Indo-Pacific, where it served a key role in the U.S. effort to bolster defense ties with Japan and other partners in the region.

The departure of USS Ronald Reagan — one of America’s largest warships and a nuclear-powered Nimitz-class aircraft carrier — comes at a time of growing tension in the face of increasingly assertive China in the Indo-Pacific .

It will be replaced later this year by USS George Washington, another Nimitz-class carrier, now on assignment near South America. Japan has been accelerating the buildup of its military capability and significantly increased joint naval operations with the United States.

Family members and friends of the crew were on hand to wave the carrier off from Yokosuka Naval Base after its final patrolling mission earlier in the day.

Hundreds of sailors stood along the rails while others on the flight deck stood forming the Japanese saying “dewa mata,” or “see you.” The carrier was accompanied by two guided-missile destroyers, USS Robert Smalls and USS Howard. It is scheduled to transit in Bremerton, Washington, later this year, before heading to a next home port assignment.

Speaking at the ceremony, U.S. Ambassador to Japan Rahm Emanuel ensured a “seamless transition.”

“The USS Ronald Reagan and her crew have ensured that millions of people across the Indo-Pacific have been able to live their lives free of coercion, aggression and suppression,” Emanuel later told reporters.

USS Ronald Reagan first arrived in Yokosuka in 2015. Earlier, during its deployment near the Korean Peninsula, the carrier contributed in Operation Tomodachi, following the 2011 earthquake, tsunami and nuclear disaster in northeastern Japan.

USS Ronald Reagan was the only American aircraft carrier deployed as a flagship of the Carrier Strike Group 5 under the U.S. Navy’s 7th Fleet, to a home port outside the U.S.

During its tenure, it participated in dozens of multilateral exercises and visited more than a dozen foreign ports, including its historic port call to Da Nang, Vietnam, last year.

While tensions have escalated in the South China Sea between China and the Philippines and a number of other countries over maritime and territorial disputes, Japan is concerned about its dispute with China over uninhabited islands in the East China Sea.

Japanese and Chinese coast guard ships repeatedly face off in the waters there.

Former Defense Minister Tomomi Inada, who recently joined an environmental survey trip near the disputed Senkaku islands, which Beijing calls the Diaoyu, said Thursday that cooperation with the U.S. and other like-minded countries is key to defending the international order.

“We have a sense of urgency that we must not let the East China Sea become another South China Sea,” she said.

Landing on the islands is not permitted, so Inada’s group flew drones for land and vegetation survey of the area. China protested the trip.

Inada said experts should be able to land on Japan’s territory for research, calling for a parliamentary debate.

Yamaguchi reported from Tokyo.

Follow AP’s Asia-Pacific coverage at https://apnews.com/hub/asia-pacific

Top headlines by email, weekday mornings

Get top headlines from the Union-Tribune in your inbox weekday mornings, including top news, local, sports, business, entertainment and opinion.

You may occasionally receive promotional content from the San Diego Union-Tribune.

More in this section

Nation-World

Golfer’s prompt release from jail rankles some who recall city’s police turmoil

World No. 1 golfer Scottie Scheffler’s arrest and prompt release from a Kentucky jail is rankling some who question whether he was given preferential treatment because of his fame

What to do when facing extended summer power outages

Texas officials say power outages could last weeks in parts of Houston after thunderstorms with hurricane-force winds tore through the city and killed at least four people

A murderous romance or frame job? Things to know about Boston’s Karen Read murder trial

The trial of a woman charged in the death of her Boston police officer boyfriend is finishing its third week

An unusual autumn freeze grips parts of South America, giving Chile its coldest May in 74 years

Chileans are bundling up for their coldest autumn in more than 70 years mere days after sunning in T-shirts

US security alert warns Americans overseas of potential attacks on LGBTQ events

The State Department has renewed a global security warning for Americans overseas and added to it that LGBTQ people and events in particular face an “increased potential for foreign terrorist organization-inspired violence.”

Upside-down flag at Justice Alito’s home another blow for Supreme Court under fire

When an upside-down U.S. flag flew over the home of Supreme Court Justice Samuel Alito in January 2021, it was largely seen in connection with the false claim by then-President Donald Trump’s supporters that the 2020 election had been marred by fraud

China reportedly suspends Japan seafood exporters' registrations

NHK has learned that Chinese authorities have suspended the registrations of facilities used by Japanese exporters of seafood.

Japanese firms seeking to export marine products to China are obliged to register their processing, storage and other facilities in Japan with Chinese customs authorities.

In August last year, the authorities suspended imports of Japanese seafood, following a release of treated and diluted water from the damaged Fukushima Daiichi nuclear power plant into the sea.

Sources familiar with the matter say the registrations of exporters' facilities had been effective until last month.

Other sources close to the Japanese government say the Chinese authorities suspended all the registrations this month.

They say the Chinese side has not provided any explanation to Japan for the latest move.

This comes as the governments have held talks on the release of the treated and diluted water this year.

The government sources say they need to find out why China chose this time to suspend the registrations.

The Fukushima Daiichi nuclear power plant suffered a triple meltdown following the 2011 earthquake and tsunami.

Water used to cool molten fuel at the plant has been mixing with rain and groundwater.

The accumulated water is treated to remove most radioactive substances, but still contains tritium.

Before releasing the treated water into the ocean, the plant's operator dilutes it to reduce tritium levels to about one-seventh of the World Health Organization's guidance level for drinking water.