Japan’s March 11, 2011 Tohoku Earthquake

slip map of 2011 Taiheiyou earthquake Japan’s 2011 Tohoku Earthquake is located at the boundary between the Pacific plate and the North American plate (this is not a typo!). These plates are converging at about 8 cm/year.

The rectangle in the figure shows the location and length of the rupture zone. The red star indicates the epicenter. The rupture was bilateral, i.e., it spread away from the epicenter in both the north and south directions, taking about 2 minutes to cover a total of 400 km (250 miles). This magnitude 9.0 earthquake was more than 500 times stronger than the recent January 12 Haiti earthquake.

The colors show the slip amplitude (i.e., the amount by which the land on one side of the fault moved with respect to the land on the other side). The motion was mainly thrust-fault (see animation).

The rupture originated about 24 km (15 miles) below the surface. In some places, the slippage along the fault was as large as 30 meters (100 feet), shown by red-shaded areas. The coast of Japan sprang east, into the ocean, in some places by as much as 5 m (16 feet).

The sea floor offshore North Honshu was thrust up and seaward, creating a devastating tsunami (SEE ANIMATION). The tsunami hit the coast of Honshu within tens of minutes and propagated across the whole Pacific, hitting Hawaii and the coast of California in about four hours and 10 hours, respectively, after the mainshock (SEE SIMULATION).

First large observational study (published in the journal Science, May 19, 2011) reveals surprising findings about energy distribution over the fault slip and stress accumulation in the Japan Trench: The length of the rupture was significantly smaller than expected for such a large earthquake; Seismic waves of different frequencies came from different areas of the fault; The strain associated with the fault slip was 10 times greater than expected for this area of the Japan Trench (press release | Science highlight | Science article)
Earthquakes: The lessons of Tohoku-Oki - An exceptional data set documents surface deformation before, during, and after the earthquake that struck northeastern Japan in March 2011. But models for assessing seismic and tsunami hazard remain inadequate. (Science News and Views article)

Preliminary Results:

Slip map - Source model derived from teleseismic body waves (preliminary) and GPS data (updated) Rupture propagation - Direct imaging of the rupture from back propagation of seismic waves Land motion - Displacement and velocity during the first 35 minutes after rupture initiation
Radiation pattern - High frequency analysis from global seismic stations Tsunami propagation simulation InSAR displacement results

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Last updated: December 5, 2011 :: Contact Us


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