Sediment effect on the tsunami generation of the 1896 Sanriku tsunami earthquake

Yuichiro TANIOKA1), and Tetsuzo SENO2)

2)Earthquake Research Institute, University of Tokyo
1)Seismology and Volcanology Department, Meterological Research Institute

Submitted to Geophys. Res. Lett., March, 2001

The 1896 Sanriku earthquake is one of the most devasting tsunami earthquakes which generates anomalously larger tsunami than expected from its seismic waves. Previous studies indicate that the arthquake occurred beneath the accretionary wedge near the trench. It was pointed out recently that sediments near a toe of an inner trench slope with a large horzontal movement on a deollement due to the earthquake might have caused an additional uplift. In this paper, the effect of the addtional uplift to the tsunami generation of the 1896 Sanriku tsunami earthquake is quantified. We estimated the slip of the earthquake by numerically computing tsunamis and comparing their waveforms with those recorded at three tide gauges. The estimated slip for the model without the addtional uplift is 10.4 m, and those with the addtional uplift are 6.7 - 6.8 m. This indicated that the addtinal uplift of the sediments near the trench has a large effect on the tsunami generation.