Sediment effect on tsunami generation of the 1896 Sanriku tsunami earthquake

The 1896 Sanriku earthquake was one of the most devastating tsunami earthqu akes, which generated an anomalously larger tsunami than expected from its seismic waves. Previous studies indicate that the earthquake occurred benea th the accretionary wedge near the trench axis. It was pointed out recently that sediments near a toe of an inner trench slope with a large horizontal movement due to the earthquake might have caused an additional uplift. In this paper, the effect of the additional uplift to tsunami generation of th e 1896 Sanriku tsunami earthquake is quantified. We estimate the slip of th e earthquake by numerically computing tsunamis and comparing their waveform s with those recorded at three tide gauges. The estimated slip for the mode l without the additional uplift is 10.4 m, and those with the additional up lift are 5.9-6.7 in. This indicates that the additional uplift of the sedim ents near the trench has a large effect on the tsunami generation.