2011 Tōhoku Earthquake and Tsunami

On March 11, 2011, at 14:46:24 JST, Japan was struck by one of the most powerful seismic events in recorded history. The 2011 Tōhoku earthquake, a massive megathrust event, triggered a devastating tsunami that affected the entire Pacific Rim. With a magnitude ranging between 9.0 and 9.1, the earthquake lasted for approximately six minutes, causing widespread destruction across northeastern Japan and beyond.

The disaster was the result of a sudden release of energy at the convergent boundary between the Pacific plate and the Okhotsk microplate. This movement occurred at a depth of 29 km (18 mi), creating a massive displacement of the seafloor that pushed a colossal volume of water toward the coastline.

A seismogram recorded in Massachusetts, United States

Key Facts

Satellite image shows snowfall on agricultural fields in Sendai area. See § Weather conditions paragraph for details.

Magnitude: 9.0–9.1 Mw
Epicenter: 38°19′19″N 142°22′08″E
Maximum Tsunami Height: 40.5 meters (133 ft) in Miyako, Iwate
Casualties: 19,759 deaths, 6,242 injured, and 2,553 missing
Economic Impact: Approximately US$360 billion in damages
Maximum Intensity: JMA 7 (MMI IX)

Geological Mechanism and Ground Motion

The earthquake is classified as a megathrust event, characterized by low-angle thrusting on a west-dipping fault plane. This type of faulting occurs when one tectonic plate is forced under another, building immense pressure until the rock ruptures.

A visual depiction of the type of faulting that caused the main tremor, low-angle thrusting on a west-dipping fault plane

The seismic energy was felt across a vast area. The Japan Meteorological Agency (JMA) recorded the highest intensity, JMA 7, in Miyagi Prefecture. Other regions, including Fukushima, Ibaraki, and Tochigi, experienced JMA 6+, while shaking was felt as far as Hokkaido and various western prefectures. The peak ground acceleration reached 2.99 g, with a peak velocity of 117.41 cm/s.

Seismic intensity observations resulting from mainshock

Hypocentral Region and Aftershocks

The hypocentral region—the area where the rupture originated—was centered off the coast of Tōhoku. Following the mainshock, the region experienced a prolonged period of seismic instability, with 13,386 aftershocks recorded as of March 6, 2018.

Hypocentral region boundaries (source: the Japanese Headquarters for Earthquake Research Promotion)

Tōhoku earthquake and aftershocks from 11 to 14 March

The Tsunami and Coastal Impact

The most lethal aspect of the disaster was the resulting tsunami. The waves traveled across the Pacific Ocean, reaching as far as the west coast of the United States and Chile. In Japan, the tsunami overtopped sea walls and floodgates in numerous locations, though some areas, such as Fudai in Iwate, were spared due to a 15.5-meter (51 ft) floodgate.

Water column height on 11 March 2011 at DART Station, 690 NM southeast of Tokyo

Run-up heights—the maximum vertical height above sea level reached by the water—were staggering. In the port of Ōfunato, the run-up height reached 24 meters (79 ft), while the fishery port of Onagawa saw waves of 15 meters (49 ft). The tsunami caused extensive flooding at the Sendai Airport and destroyed nearly the entire lower area of Rikuzentakata.

The city of Rikuzentakata, Iwate Prefecture, suffered extensive damage from the tsunami, with almost the entirety of the lower area of the city being destroyed.

While the tsunami was able to surmount sea walls and floodgates in many areas along the coastline of the Tohoku region, Fudai, Iwate, was spared destruction due to its 15.5-meter (51 ft) floodgate, which successfully withstood the waves.[153]

Tsunami flooding on the Sendai Airport runway

Peak tsunami wave height summits, color-coded with purple representing most severe

Global Reach and Environmental Effects

The energy of the tsunami was detected globally. Debris from the disaster, including a Japanese boat, eventually washed ashore on the United States' west coast. The event also caused ecological disruptions, such as the trapping of a Bonin petrel on Midway Atoll.

A Bonin petrel trapped in tsunami debris on Midway Atoll before being rescued

Fishing boats that were moved to higher ground in anticipation of tsunami arrival, in Pichilemu, Chile

A Japanese boat that washed ashore on the west coast of the United States, now preserved at the Columbia River Maritime Museum

Secondary Effects and Infrastructure Damage

A loose cow roaming through Namie, Fukushima after the area was evacuated

Beyond the immediate impact of the waves, the disaster triggered several secondary catastrophes. Soil liquefaction—a process where saturated soil loses strength and behaves like a liquid—was observed in Kōtō, Tokyo, and Urayasu, Chiba.

Land subsidence and soil liquefaction at Shin-Urayasu Station in Urayasu, Chiba, near Tokyo

Significant land subsidence occurred along the coast, with the Oshika Peninsula in Miyagi sinking by as much as 1.2 meters (3 ft 11 in). Other coastal towns like Rikuzentakata and Kamaishi saw subsidence between 0.66 and 0.84 meters.

Energy and Industrial Failures

The disaster crippled Japan's energy infrastructure. Damage to transmission towers and power lines was widespread, particularly in Minamisōma. The event also caused fires at the Cosmo Oil refinery in Ichihara and the Sendai Nippon Oil refinery. Most critically, the disaster led to the Fukushima nuclear meltdowns, resulting in significant radiation leaks.

Geographic divide between 50 hertz systems and 60 hertz systems in Japan's electricity distribution network

A damaged transmission tower and severed power lines in Minamisōma, Fukushima

Fire at the Cosmo Oil refinery in Ichihara

An aerial view of the smoke from the Sendai Nippon Oil refinery

Fukushima radiation comparison to other incidents and standards, with graph of recorded radiation levels and specific accident events (Note: Does not include all radiation readings from Fukushima Daini site.)

Transport and Urban Destruction

Infrastructure failures included the collapse of highway bridges and the destruction of railway stations, such as Shinchi Station. Rescue efforts were further hampered by unexpected weather conditions, as snowfall arrived in areas like Ishinomaki and Kamaishi shortly after the tsunami struck.

VA-TF1 Rescue team from Fairfax County, Virginia searching for survivors in Kamaishi, Iwate Prefecture. Snow arrived minutes before or after the tsunami, depending on locations.[40]

Snowfall in Ishinomaki, 16 March. Snow fell across several areas where the tsunami struck, further worsening the conditions and hampering rescue efforts.

A damaged crane stands next to a ship lifted onto the docks at Sendai's port.

Summary of Impact by Prefecture

Damage to a traditional lantern at Tokiwa shrine in Mito City

Prefecture	Fatalities	Missing	Injuries	Destroyed Houses
Miyagi	10,567	1,217	4,148	83,005
Iwate	5,145	1,111	213	19,508
Fukushima	3,931	224	183	15,435
Ibaraki	66	1	714	2,638
Tochigi	4	133	261	2,118

Frequently Asked Questions

What caused the 2011 Tōhoku earthquake?

The earthquake was caused by a megathrust rupture at the convergent boundary where the Pacific plate subducts beneath the Okhotsk microplate.

How high were the tsunami waves?

While many areas saw waves between 10 and 20 meters, the peak tsunami height reached 40.5 meters (133 ft) in Miyako, Iwate.

What is land subsidence and did it occur here?

Land subsidence is the sinking of the Earth's surface. It occurred significantly along the Tōhoku coast, with the Oshika Peninsula sinking by 1.2 meters.

How many people were affected by the disaster?

The disaster resulted in 19,759 deaths, 2,553 missing persons, and 6,242 injuries, with over 122,000 houses completely destroyed.

Did the earthquake affect areas outside of Japan?

Yes, the tsunami traveled across the Pacific Ocean, causing damage and observations as far away as the United States, Chile, and Norway.