Tsunami run-up associated with co-seismic thrust slip produced by the 2011 Mw 9.0 Off Pacific Coast of Tohoku earthquake, Japan

Abstract

The 2011 Mw 9.0 Off Pacific Coast of Tohoku (Japan) earthquake generated a violent tsunami and unexpected high tsunami wave that caused great substantial damage and ∼18,940 fatalities along the east–northeast coast of Honshu Island of Japan. Analyses of high-resolution remote sensing imagery data acquired before and after the earthquake, combined with the results of field investigations, reveal that (i) run-up height of the tsunami (i.e., the inland limit of tsunami) was spatially variable, ranging from <3m to ∼35m, and (ii) large run-up heights occurred mainly in the areas between Ishinomaki (∼38.2°N) and Miyako city (∼40.2°N), close to the epicenter of 2011 Mw 9.0 earthquake, and showed a gradual decrease away from this region. Combined with the ground motion direction revealed by GPS and seismic data, the distribution of run-up height is consistent with that of ground displacement (calculated from GPS observations) and that of co-seismic thrusting slip on the source fault plane along the plate boundary (calculated from the seismic inversion). The results of numerical simulation of tsunami propagation show that (i) the distributions of tsunami height along the northeast Honshu coastline are constrained mainly by thrusting slip on the source fault plane; and (ii) the height of tsunami wave in special areas was strongly affected by the sawtooth geometry of the coastline.