It happened along the Kego Fault zone.
The magnitude 9.0 Tohoku earthquake on March 11, 2011, which occurred near the northeast coast of Honshu, Japan, resulted from thrust faulting on or near the subduction zone plate boundary between the Pacific and North America plates.
On March 11, 2011, a magnitude 9.0 earthquake occurred near the east coast of Japan, which triggered a massive tsunami. UPDATE: Official magnitude was updated to 9.1 on Nov 7, 2016.
Because the the pacific plate and Eurasian plates where stuck near japan and built up pressure along that fault line and eventually the pressure released and caused the earthquake to happen.
The epicenter for the magnitude 9.0 earthquake in Japan on March 11, 2011 was reported to be 129 kilometers (80 miles) off the east coast of the Oshika Peninsula, Tōhoku, near Sendai.
The Northeastern coast of Japan . Note: Their Nuclear Power Plants released chemicals into the air because of the earthquake. VERY VERY BAD!!!! (May affect LA)
The location for the magnitude 9.0 earthquake in Japan on March 11, 2011 was 129 kilometers (80 miles) off the east coast of the Oshika Peninsula, Tōhoku, near Sendai at a depth of 32 kilometers (20 miles).
The magnitude 9.0 Tohoku earthquake on March 11, 2011, which occurred near the northeast coast of Honshu, Japan, resulted from thrust faulting on or near the subduction zone plate boundary between the Pacific and North America plates.
Japan is near to a fault line.
When small earthquakes result in a volcano, they are caused by a slip on a fault near an existing volcano. In 1981, the largest felt volcanic earthquake occurred in the Cascades.
The earthquake on March 11, 2011 occurred in the depths of the Pacific Ocean near the northeast coast of Honshu, Japan, about 130 kilometers (80 miles) east of the city of Sendai.Exact location: 38.297°N, 142.372°E
The magnitude 9.0 Tōhoku earthquake on March 11, 2011, occurred in the depths of the Pacific Ocean near the northeast coast of Honshu, Japan, about 130 kilometers (80 miles) east of the city of Sendai. Exact location: 38.297°N, 142.372°E
Japan is near a very active fault zone where earthquakes and volcanoes occur often. On March 11, 2011 alone, there were 200+ aftershocks. From the 9.0 magnitude earthquake on Friday March 11 05:46:23 UTC until March 31 midnight there were approximately 2,806 earthquakes ranging in magnitude 3.9 through 7.9. As of August 10 there were 4,308 earthquakes in or near Japan for year 2011 according to the USGS earthquake data (not including small quakes under M 3.0) with March the most active month of the year.