Japan earthquake in HONSHU, JAPAN 2011 March 11 05:46:23 UTC

by **Admin** on Fri Mar 11, 2011 5:29 pm

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 230 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 75 km to the southwest caused 22 fatalities
and over 400 injuries. In December of 2008, a sequence of 4 moderate
earthquakes (M 5.3-5. Cool

occurred within 20 km of the March 11 event. In
the first 12 hours following the March 11 earthquake, the region has
experienced over a dozen aftershocks of M 5 or greater, the largest
being M 5.7.

Japan earthquake in HONSHU, JAPAN 2011 March 11 05:46:23 UTC 40_140