Estimation of Runup Heights of the 2011 off the Pacific Coast of Tohoku Earthquake Tsunami Based on Numerical Simulations

ABSTRACT

A strong earthquake (M9.0) occurred at 14 h 46 m (JST) on March 11, 2011 in the Pacific Ocean east of the Tohoku district in the northeast part of Honshu Island, Japan. The earthquake was accompanied by a large tsunami. The main goal of this study is to use numerical modelling to reproduce the observed characteristics of the 2011 tsunami. First, the water elevation records of DART buoys, coastal tidal gauges and GPS wave buoys are compared with the numerical simulation. Then, the observed runup heights that were published by the Joint Survey Group are compared with the results of the numerical simulations in the Pacific coast of the Tohoku district. For tsunami modelling in ocean and coastal zone, numerical computations were performed with the Princeton Ocean Model (POM). The finite fault model of the U.S. Geo-logical Survey is chosen to reproduce the tsunami source. For computing the runup height, the time series of the water height that were determined by the numerical model in the last sea grid points were converted by the 1D analytical nonlin-ear theory of long-wave runup. The computed runup heights on the shore roughly correlate with the observed runup heights, with the exception of the northern Miyagi Prefecture, which was directly hit by the tsunami.