Characteristics of great earthquakes occurring in the central Kuril Islands

高橋, 浩晃; 前田, 宜浩; 笠原, 稔

Characteristics of great earthquakes occurring in the central Kuril Islands | 中千島で発生した巨大地震

2009

高橋, 浩晃 | 前田, 宜浩 | 笠原, 稔

We investigate the characteristics of great earthquakes occurring in the central Kuril Islands on 1915, 1918, 2006 and 2007. Comparisons of seismic intensity distributions, tsunami data and waveforms of above four events were made. Though magnitudes of these earthquakes were almost the same, only the 1915 event did not generate observable tsunami. This fact may be due to deep focal depth of this earthquake. Similarities of seismic intensity distributions between the 1915, 1971 and 2008 deep-focus earthquakes also imply that the 1915 event was the deep-focus event in the northeastern Okhotsk Sea. Waveform properties of the 1915 and 2008 events supports above hypothesis. We conclude, therefore, that the 1915 earthquake was not the event in the central Kuril Island but in the Okhotsk Sea with deep depth. Large tsunami and widespread felt area of the 1918 earthquake show that this event was a typical shallow-dipping thrust event on plate boundary as indicated by previous studies.

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