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Mw 9.0 off the Pacific coast of Tohoku, Japan Earthquake, on March 11th, 2011 at 05:46 UTC

Last update: 27 February 2012 at 13:23 UTC

Earthquake details | Liquefaction | Felt & Damage reports | Tectonic settings | Tsunami information | Aftershocks locations

Seismograms showing the Earth' normal modes | Send us pictures or videos | Epicenter location

Earthquake details

On March 11th, 2011, an earthquake of magnitude Mw 9.0 occurred off the Pacific coast of Tohoku, Honshu Island, Japan, at 14:46 local time (05:46 UTC.) More information here. It has been followed by a series of powerful aftershocks, with 31 earthquakes of magnitude larger than 6 in 3 days.

The earthquake epicenter is located approximately 100 km off Miyagi at a depth of 22km. It was widely felt as far as Tokyo, about 400 km away. A tsunami wave was generated in the Pacific, with wave heights reported at more than 4 m high. The Yomiuri daily newspaper reports that the tsunami waves reached at least 23m according to a study by the Port and Airport Research Institute in Ofunato (Iwate prefecture).

This is the largest earthquake ever recorded in Japan, and is among the 5 largest earthquakes recorded worlwide.

Two days earlier, on March 9th, another large earthquake occurred in the same area, approximately 35 km away from the main earthquake March 11th. More information is available at the EMSC and at the USGS.

On April 7th (14:32 UTC), a strong aftershock (Mw 7.1) occurred 50km west of the main shock.

Peak ground acceleration recorded by the japanese network (NIED) Along the coast, horizontal maximum accelerations have been recorded (in red) with values above 2g. A maximum of 2.7g was recorded at station MYGO4.

Peak Ground Acceleration (NIED) Acceleration recorded at station MYG004 displaying the largest PGA measured (this KNET station is located near Kurihara)

Observed (black) and predicted (red) horizontal GPS displacements (Caltech- JPL ARIA group)

More information here:

http://www.tectonics.caltech.edu/slip_history/2011_taiheiyo-oki/

The Harvard University has computed the Energy Distribution of the earthquakes sequence extending along the Coast from Iwaki to Kesennuma. Most of the energy off shore was released in front of Sendai, which could explain the strength of the tsunami and its strong impact in this area.

Additionnally, this city is situated on low lands surrounded by mountains.

Source: Eric Kizer, Harvard University, USA



A preliminary modelisation of the USGS gives a surprisingly short rupture length of about 300 km along strike, with a southward direction along the Japan Trench and 150 km downdip. The displacement is evaluated to 17m. If this rupture length is confirmed, it proves to be short for a magnitude 9 earthquake.

Preliminary USGS rupture modelisation

Caltech University confirms this hypothesis with a 300 km rupture length but with a displacement of 30m.

Preliminary Caltech rupture modelisation

More information:

General information:

EMSC mainshock information

USGS special publication

Iris Teachable moment presentation

IPGP (Paris, France) special web page

ERI (Earthquake Research Institute - University of Tokyo, Japan) web page

IISEE (International Institute of Seismology and Earthquake Engineering, Japan) web page

CEA/LDG special web page (in french)

IRSN (France) note on the Japanese seismic event (in french)

AFPS (French Association for Earthquake Engineering) dedicated web page

Additional scientific information on this event are available at GEO Geohazards Supersite including GPS, Ground Motion, Slip distribution

More scientific & public information (ERI)

Institut des Sciences de la Terre special page (in french)

CNRS/INSU special page (in french)

Comments on the earthquake

Specific analysis:

Fast teleseismic body-wavesource inversion (by Martin Vallee; Geoazur, Nice, France)

Preliminary modeling of the source of the March 11, 2011, by retro-propagation of P waves (Claudio Satriano – IPGP)

Mainshock location, magnitude and tsunami potential determinations in real-time at INGV (Alberto Michelini, INGV, Anthony Lomax, ALomax Scientific)

The Earth eigenmodes excited by the Japanese earthquake (by van Camp and Rivera; ROB and EOST, Belgium and France)

Co-seismic displacement at surface using the USGS epicentre + slip model and an Okada code for elastic deformations and Coulomb stress transferred on optimal planes to regional compression (N115E) using the USGS epicentre + slip model and the code DLC (from Bob Simpson, USGS) (A. Ganas, NOA, Greece)

Co-seismic displacements at two japanese stations (K.Chousianitis and A. Ganas, GEIN, NOA, Greece)

National Seismic Hazard map for Japan (2005)

Preliminary slip model using Strong Motion stations and ISOLA code (J. Zahradnik, F. Gallovic, CUNI, Czech Republic and E. Sokos, G-A Tselentis, UPatras, Greece).



Liquefaction effects

Liquefaction effects have been observed in several places in Japan. (Updated 2011-04-11)

Felt & Damage reports

Witnesses report that the shaking lasted for about 2 minutes. It was largely felt across the entire Honshu Island, and as far away as Osaka.

Massive damage has been reported, mainly related to the subsequent tsunami.

The nuclear power plant of Fukushima has been strongly affected by the tsunami. More information about the nuclear accident are available at:

IRSN note on the nuclear power plant situation (in french)

IAEA note on the seismic and nuclear situation

Video: Shaking Yokoama (Source: Le Post)

Satellite photos before and after the earthquake (Source: New York Times) and here (Source: Media Tools)



JMA has issued a map of intensity showing a maximum for Kurihara City of Miyagi Prefecture JMA Seismic Intensity Scale

More information on the JMA scale

MEGA DISASTER IN A RESILIENT SOCIETY: (updated 2011-04-11)

The International Environment and Disaster Management Laboratory of Japan has published a detailed report on the earthquake and its consequences, adressing the major challenge of disaster risk reduction. The report provides scientific observations, damages information, humanitary organisation (rescue and shelter), as well as the expected economic impact for Japan. The aim of the report is to synthesize certain existing data with basic situation analysis.

Tectonic settings

The earthquake involved a thrust fault with displacement up to 15 m.This region is located on the subduction zone boundary where the Pacific Plate subducts beneath the Eurasian Plate. The pacific plate moves approximately westward with respect to the North American plate at a velocity of 83mm/year.

More information are available here: http://pubs.usgs.gov/of/2010/1083/d/



Scheme of the Eurasia-Philippine Sea-Pacific triple point Source: USGS The 03/11/2011 earthquake occurred near the east coast of Honshu, it is the result of thrust faulting about 200km west of the subduction zone (Japan Trench). This boundary corresponds to the Pacific plate diving below the Eurasian plate Source: Modified from: L. Jolivet, ISTO, Orléans, France The Philippine Sea Plate, supporting the Bonin Arc, dives beneath the Eurasian plate at the Nankai Trench.

The Pacific plate dives under the two previous plates in the Japan and Bonin Trenchs.

In fact, the northern part of Japan belongs to the North American plate but the relative displacement between the Eurasian and the North American plates in this region is relatively low.

The previous major event in the region occurred on March 2nd, 1933 with magnitude Mw 8.4 on the Sanriku coast, which also generated an important tsunami. It was located 140 km North East of the 2011 March 11th earthquake.

In January, 1995, a magnitude 6.8 earthquake occurred nead Kobé (West of Japan), which was the most damaging and deadly earthquake in Japan at that time.

Tsunami information

The major aftermath tsunami has swept Japan and the Pacific Ocean. More details are available at the NOAA Center for Tsunami Research: http://nctr.pmel.noaa.gov/honshu20110311/ The buoy measurements report a 7.3m high wave in Soma, south of Sendai according to JMA. This is highest wave measurement ever. Several instruments, among which one in Fukushima have been destroyed. This tsunami has devastating consequences in the region of Sendai and Northern Honshu. However the wave travelling across the Ocean, reaching Hawaii, French Polynesia or the Coast of Northern and Southern Americas has not generated significant damages.

The Japan Meteorological Agency provides more information about the tsunami. Tsunami Travel Time Modelisation for the Honshu earthquake (Hélène Hébert, CEA, France) The wave travels over the whole oceanic system, reaching the Atlantic approximately 20 hours after the earthquake.

Source: BBC

Japan Meteorological Agency Tokyo, Japan

Pacific Tsunami Warning Centre Hawai, USA

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