Looking back, looking forward: Fifteen years after Tōhoku

The most powerful earthquake ever recorded in Japan, and a trigger for tsunami waves that reached nearly 50 feet (15 meters) tall, the memory of the M9.0 earthquake that occurred offshore of the east coast of the Tōhoku region on the island of Honshu, Japan, on March 11, 2011, at 2:46 p.m., remains deep among those who experienced it.

A rare event, it still provides a once-in-a-generation opportunity for those involved in understanding catastrophic events to learn and to continue pushing the boundaries of earthquake science and engineering.

With an epicenter in the Pacific Ocean some 80 miles (130 kilometers) east of Sendai and 230 miles (370 kilometers) northeast of Tokyo, ground shaking across many areas lasted for over five minutes, reaching Tokyo.

An event of this size was not anticipated. The 450-year historical earthquake record for the Japan Trench did not contain earthquakes comparable to the 2011 event in this region. The 'maximum credible earthquake’ along this section of the Japan Trench was previously considered to be M8.3.

An earthquake so big that the Earth’s Day shortened by 1.8 microseconds and shifted its figure axis by 7 inches (17 centimeters), the Tōhoku M9.0 earthquake was located on the subduction interface plate boundary where the Pacific Plate is driven underneath Japan along the Japan Trench.

A plate boundary that had historically generated independent, smaller-sized earthquakes ruptured 250 miles (400 kilometers) due to a cascade of events on several adjacent fault ruptures. The maximum fault displacement for the earthquake has been estimated at 100 to 130 feet (30 to 40 meters), explaining the strong ground motions radiated from the source and the extensive inundation zone generated by the tsunami.

Tsunami

This vertical displacement of the sea floor, associated with an unusually large underlying fault movement, triggered tsunami waves that propagated westward toward the Japan coastline and eastward across the Pacific Ocean, impacting the eastern coast of the Tōhoku region.

Waves reached the coast of Japan within 10 minutes of the earthquake, on a typical Friday afternoon of work and school. Coastal areas within Iwate, Miyagi, and Fukushima Prefectures experienced waves of over 16 feet (5 meters); in some areas, waves were above 33 feet (10 meters), e.g., Miyako District in Iwate Prefecture; and in localized areas, waves were more than 49 feet (15 meters), e.g., Ōfunato District in Iwate Prefecture.

The locations with the highest inundation depths were associated with deep, funnel-shaped embayments focused on the tsunami waves.

Three mechanisms

The impacts of the 2011 Great East Japan Earthquake and Tsunami were driven by three mechanisms: strong ground shaking from the M9.0 earthquake, extensive tsunami inundation, and a significant nuclear accident triggered by the tsunami waves at the Fukushima Daiichi power plant, located on the coast, some 40 miles southeast of Sendai.

Image: Joban Expressway: Section close to the Fukushima Daiichi nuclear power plant features an electronic display board showing radiation levels (2.2 microsieverts)

Using the Shindo scale, also known as the Japan Meteorological Agency (JMA) Seismic Intensity Scale, Kurihara City in Miyagi Prefecture had the highest possible intensity of JMA7. Twenty-eight cities and towns in Miyagi, Fukushima, Ibaraki, and Tochigi Prefectures experienced JMA6+ intensity, causing significant damage over a large area.

The scale of the destruction is chilling. Government statistics show that more than 122,000 buildings were destroyed, 288,000 were very significantly damaged, and more than 749,000 were partially damaged.

In addition, there was extensive damage to infrastructure and lifelines, including 4,200 damaged road sites, 116 damaged bridges, and 29 locations experienced railway damage.

The World Bank estimated the economic impact at up to US$235 billion, still the highest economic loss from a natural disaster ever observed. For the local and international insurance and reinsurance communities, the earthquake and tsunami were a significant insurance loss estimated at US$35 billion, making it the largest earthquake insurance loss in history.

Loss of life

In addition to the extensive property damage and economic disruption, the event took a large toll on the human population. Nearly 20,000 people died, the majority (91%) having drowned due to the tsunami. Additional deaths resulted from fires, being crushed in buildings, and other causes.

Approximately two-thirds of those killed were over 60 years old, but deaths were reported for all ages. In addition to the many fatalities, there were approximately 6,200 injuries resulting from a variety of causes.

At recent memorial services across Japan on March 11, 2026, marking the 15th anniversary with a moment of silence at 2.46 p.m., communities reflected on the suffering caused by extensive damage across the Tōhoku region due to the earthquake's ground motions and tsunami inundation.

For Fukushima Prefecture in particular, the recovery is long and arduous, as 26,281 people remain designated evacuees and are unable to return to their homes.

Seven municipalities in the prefecture still have evacuation orders in effect, due to the nuclear fallout from the accident. The government announced the Reconstruction Agency’s third five-year phase of reconstruction and revitalization of Fukushima Prefecture, set to begin on April 1, 2026.

The Reconstruction Agency, originally intended to be a temporary governmental body, has had its mandate extended several times. Its current 'final' expiration is set for March 2031, marking exactly 20 years since the disaster, though ongoing decommissioning in Fukushima is projected to last until at least the 2050s.

At a regular news conference on March 11, 2026, Chief Cabinet Secretary Minoru Kihara said:

“Upon the determination that there can be no recovery of Tōhoku without the recovery of Fukushima, and with that, no revival of Japan as a whole, we will work to address a wide range of challenges over the next five years.”

Because major earthquake disasters are so infrequent, it is essential to utilize available data to improve the representation of seismic risk. The understanding of seismic risk in Japan has been fundamentally improved thanks to the learnings from this event.

The extensive research and observation data from the 2011 earthquake and tsunami provided the scientific and engineering communities with the opportunity to delve deeper into megathrust earthquakes and their impacts.

For example, Japan’s dense network of seismic stations generated extensive ground-motion observations, enabling a comprehensive analysis of ground-motion attenuation and frequency content, site amplification, and basin characteristics.

From a modeling perspective, we updated our modeling in 2012, and our initial high-definition Moody's RMS® Japan Earthquake and Tsunami HD Model was launched in 2018. Without the wealth of data from Tōhoku, scientific advances, and comprehensive damage statistics linked with ground-motion observations and tsunami inundation depths, the calibration of building vulnerability functions would not be at the level it is today.

New modeling being completed this year will extend the scope of this peril model to include mortality and morbidity assessment of the human population. Users will be able to consider the impacts of the shake, fire, and/or tsunami, generating the resulting injury severity distribution.

As the years pass, we mourn the ~20,000 people who were injured or lost their lives, those who are still reported missing, and those still displaced from their towns and villages.

New construction is very mindful of the threat of major seismic events, such as the long-anticipated Nankai Trough megaquake, as reported in the Japan Times, which, in the government’s worst-case scenario, could result in as many as 298,000 deaths nationwide and widespread destruction.

From giant seawalls around the coast of Futaba, to Miyagi Prefecture, an entirely new community built inland after the tsunami, about 80 kilometers north of Futaba, Japan, is carefully planning for the future, still in the shadow of Tōhoku.

Find out more about Moody's RMS Japan Earthquake HD Model here.