High‐speed rupture in the first 20 s of the 2011 Tohoku earthquake, Japan

Abstract

AbstractThe 2011 Tohoku earthquake produced tens of meters of fault slip near the Japan Trench, which generated devastating tsunami. The rupture process before the huge slip is still unclear due to a lack of resolution. Here I perform a multiscale slip inversion analysis to examine the first 10 and 20 s of the rupture process and the whole rupture process at different scales. The result shows that 4 s after the initiation, this earthquake started with a relatively high‐speed rupture that had a peak slip rate faster than 1 m/s and a rupture velocity comparable to 3 km/s. Fourteen seconds after the initiation, the rupture propagation direction changed from northward to westward, near the edge of the M 7.3 foreshock coseismic slip area. The stress release by the foreshock may contribute to the complex small‐scale rupture propagation, which may appear to be slow rupture propagation when only looking at long‐period data.