Characteristic of Seismic Intensity and Tsunami Height on the Hokkaido-Sanriku Region, North Japan

Abstract

On the tsunamigenic earthquakes generated off the Kurile Is. to Tohoku regions during the last 98 years, 1894-1991, the characteristic of seismic intensity, tsunami frequency and tsunami height at 10 tidal stations along the Pacific coast is investigated. At the many stations, the tsunamis were most observed when the seismic intensity reaching I=4 (JMA scale). However the number of tsunamigenic earthquakes is 1/10 times or less for the frequency of earthquakes (I≥4).
According to the height-distance diagram for the Kurile-Hokkaido tsunamis, the observed tsunami heights at Hachinohe exceed more than 1.8 times higher than the heights inferred from the average tsunami magnitude. Tsunami heights along the Sanriku coast are relatively large, but those at Kushiro, Muroran and Hakodate show a tendency to be small. For the Sanriku tsunamis, the tsunami heights along the Sanriku coast nealy correspond to the tsunami magnitudes, but those in the Hokkaido region are a litlle small excep Urakawa. The deviations from the average tsunami magnitude caused by the submarine topography indicate the measure of tsunami hazards.