Tsunami source estimation for the 2011 off the Pacific coast of Tohoku Earthquake using thickness distribution of tsunami deposits in a wide area

Abstract

This study proposed a method to estimate tsunami source models based on the thickness distribution of tsunami deposits. We applied the previously-proposed Conical Fault Models as tsunami source, which considers known data of inter-plate coupling and distribution of historical earthquakes. We further proposed a new method to calculate deposition volume along survey transects, and formulated the relationship between the fault slip and the deposition volume. To validate the new method, we estimated a tsunami source model of the 2011 Tohoku-oki Earthquake (Mw 9.0) based on the data of tsunami deposits from three areas. The fault slip was in a proportional to the deposit volume, and the magnitude was estimated at close to Mw 9.0. Therefore, it was revealed that the moment magnitude of the source model of a large tsunami can be estimated from only the thickness information of the tsunami deposits.