Magnitude 8.9 - NEAR THE EAST COAST OF HONSHU, JAPAN

2011 March 11 05:46:23 UTC

Earthquake Details

This is a computer-generated message -- this event has not yet been reviewed by a seismologist.

Magnitude	8.9
Date-Time	Friday, March 11, 2011 at 05:46:23 UTC Friday, March 11, 2011 at 02:46:23 PM at epicenter Time of Earthquake in other Time Zones
Location	38.322°N, 142.369°E
Depth	24.4 km (15.2 miles) set by location program
Region	NEAR THE EAST COAST OF HONSHU, JAPAN
Distances	130 km (80 miles) E of Sendai, Honshu, Japan 178 km (110 miles) E of Yamagata, Honshu, Japan 178 km (110 miles) ENE of Fukushima, Honshu, Japan 373 km (231 miles) NE of TOKYO, Japan
Location Uncertainty	horizontal +/- 13.5 km (8.4 miles); depth fixed by location program
Parameters	NST=350, Nph=351, Dmin=416.3 km, Rmss=1.46 sec, Gp= 29°, M-type="moment" magnitude from initial P wave (tsuboi method) (Mi/Mwp), Version=A
Source	USGS NEIC (WDCS-D)
Event ID	usc0001xgp

Earthquake Summary

Earthquake Summary Poster

Tectonic Summary

The 03/11/2011 earthquake (preliminary magnitude 8.9) near the east coast of Honshu, Japan, occurred as a result of thrust faulting on or near the subduction zone interface plate boundary between the Pacific and North America plates. At the latitude of this earthquake, the Pacific plate moves approximately westwards with respect to the North America plate at a velocity of 83 mm/yr. The Pacific plate thrusts underneath Japan at the Japan Trench, and dips to the west beneath Eurasia. The location, depth, and focal mechanism of the March 11 earthquake are consistent with the event having occurred as thrust faulting associated with subduction along this plate boundary. Note that some authors divide this region into several microplates that together define the relative motions between the larger Pacific, North America and Eurasia plates; these include the Okhotsk and Amur microplates that are respectively part of North America and Eurasia.

The March 11 earthquake was preceded by a series of large foreshocks over the previous two days, beginning on March 9th with an M 7.2 event approximately 40 km from the March 11 earthquake, and continuing with a further 3 earthquakes greater than M 6 on the same day.

The Japan Trench subduction zone has hosted 9 events of magnitude 7 or greater since 1973. The largest of these was an M 7.8 earthquake approximately 260 km to the north of the March 11 event, in December 1994, which caused 3 fatalities and almost 700 injuries. In June of 1978, an M 7.7 earthquake 35 km to the southwest caused 22 fatalities and over 400 injuries.

Seismologist Bernd Weber of Germany's Geoscientific Research Institute GFZ in Potsdam poses for the media as he points on a graph with the magnitude of the earthquake in Japan on a monitor in Potsdam, March 11, 2011. The biggest earthquake to hit Japan on record struck the northeast coast on Friday, triggering a 10-metre tsunami that swept away everything in its path, including houses, ships, cars and farm buildings on fire.