A tsunami earthquake is defined as an earthquake which induces abnormally strong tsunami waves compared with its seismic magnitude (Kanamori 1972; Kanamori and Anderson 1975; Tanioka and Seno 2001). We investigate the possibility that the surface waves (Rayleigh, Love, and tsunami waves) in tsunami earthquakes are amplified by secondly submarine landslides, induced by the liquefaction of the sea floor due to the strong vibrations of the earthquakes. As pointed by Kanamori (2004), tsunami earthquakes are significantly stronger in longer waves than 100 s and low in radiation efficiencies of seismic waves by one or two order of magnitudes. These natures are in favor of a significant contribution of landslides. The landslides can generate seismic waves with longer period with lower efficiency than the tectonic fault motions (Kanamori et al 1980; Eissler and Kanamori 1987; Hasegawa and Kanamori 1987). We further investigate the distribution of the tsunami earthquakes and found that most of their epicenters are located at the steep slopes in the landward side of the trenches or around volcanic islands, where the soft sediments layers from the landmass are nearly critical against slope failures. This distribution suggests that the secondly landslides may contribute to the tsunami earthquakes. In the present paper, we will investigate the rapture processes determined by the inversion analysis of seismic surface waves of tsunami earthquakes can be explained by massive landslides, simultaneously triggered by earthquakes in the tsunami earthquakes which took place near the trenches.1)&nbsp;&nbsp;&nbsp; Kanamori, H.: Mechanism of tsunami earthquakes. Physics of the Earth and Planetary Interiors, 6, 346-359, 1972.2)&nbsp;&nbsp;&nbsp; Kanamori, H. and Anderson, D. L.: Theoretical basis of some empirical relations in seismology. Bulletin of the Seismological Society of America, 65, 1073-1095, 1975.3)&nbsp;&nbsp;&nbsp; Tanioka, Y. and Seno, T.: Sediment effect on tsunami generation of the 1896 Sanriku tsunami earthquake. Geophysical Research Letters, 28, 3389-3392, 1996.4)&nbsp;&nbsp;&nbsp; Kanamori, H., 2004: The diversity of the physics of earthquakes, proc. Jpn. Acad. Ser. B 80, 297-315.5)&nbsp;&nbsp;&nbsp; Kanamori, H. and Given, J.W., and Lay, T., 1980: Analysiso f Seismic Body W aves Excited by the Mount St. Helens Eruption of May 18, J. Geophys. Res., 89, 1856-1866.6)&nbsp;&nbsp;&nbsp; Eissler, H.K. and Kanamori, H, 1987: A Single-force model for the 1975 Kalapana, Hawaii earthquake, J. Geophys. Res., 92, B6, 4827-4836.7)&nbsp;&nbsp;&nbsp; Hasegawa, H.S. and Kanamori, H, 1987: Source Mechanism of the magnitude 7.2 Grand Banks Earthquake of November 1929: Double couple or submarine Landslide?, Bulletein of the Seismological Society of America, 77, 6, 1984-2004.

What Is Tsunami Earthquake?

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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