GEOLOGICAL SOCIETY OF THE PHILIPPINES
Mechanism of Tsunami Earthquake
Seismology and Volcanology Research Department, Meteorological Research Institute, Tsukuba 305-0052, Japan.
(Now, a JICA expert at Philippine Institute of Volcanology and Seismology)
The 1946 Aleutian and the 1896 Sanriku earthquakes are two of the most devastating tsunami earthquakes, which generated an anomalously larger tsunami than expected from its seismic waves. In this paper, the tsunami generation caused by the additional uplift due to a large horizontal movement of the backstop beneath the accretionary prism is quantified for the 1946 Aleutian and the 1896 Sanriku tsunami earthquakes. We estimate the slip of those tsunami earthquakes by numerically computing tsunamis and comparing their waveforms with those recoded at tide gauges. For both the 1946 Aleutian and the 1896 Sanriku tsunami earthquakes, the estimated slips for the model without the additional uplift are significantly larger than those with the additional uplift. This indicates that the additional uplift of the sediments near the trench has a large effect on the tsunami generation.
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