HR: 17:45h
AN: S52K-08    [PDF]
TI: The source process of the 1971 Sakhalin earthquake estimated using tsunami waveforms
AU: * Tanioka, Y
EM: tanioka@eos.hokudai.ac.jp
AF: Hokkaido University Institute of Seismology and Volcanology, Norh 10 West 8 Kita-ku, Sapporo, 060-0810 Japan
AB: On September 5, 1971, the Sakhalin earthquake (Ms 7.1) occurred off southeast coast of Sakhalin, Russia. The earthquake generated a tsunami observed at tide gauges in Sakhalin and Hokkaido. This earthquake is one of several large earthquakes occurred along the eastern margin of the Japan Sea in the last century. Other large earthquakes are the 1940 Shakotan-oki (Mw 7.5), 1964 Niigata (Mw 7.5), 1983 Japan Sea (Mw 7.9), 1993 Hokkaido Nansei-oki (Mw 7.8) earthquakes. Those earthquakes are considered to be the underthrust events occurred along the convergent boundary between the Eurasian and North American plates. The 1971 Sakhalin earthquake has not been well studied although the other large earthquakes have been studied well using both seismic and tsunami waveforms. In this paper, we studied the source process of the Sakhalin earthquake using the tsunami waveforms observed at tide gauges in Hokkaido, Japan. The tsunami waveforms are computed numerically using the finite difference method of the linear long wave equation. The grid size is basically 20 sec arc (about 600m), but finer grids (4 sec) are used around the tide gauge stations. The dip angle of the fault is assumed to be 45 degree which is typical in this region. The length and width of the fault are assumed to be 70 km and 25 km, respectively. Comparison of computed and observed tsunami waveforms shows that the slip amount of the fault is about 1.5 m. By assuming that the rigidity around the fault is 4 x 10**10 N/m2, the seismic moment is estimated as 1.05 x 10**20 Nm (Mw 7.3). The tsunami waveforms observed at tide gauges in Hokkaido, Japan, were explained by the fault model. This confirms that the Sakhalin earthquake is another underthrust event occurred along the convergent boundary existing near the eastern margin of the Japan Sea.
DE: 4564 Tsunamis and storm surges
DE: 7215 Earthquake parameters
DE: 7230 Seismicity and seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting