2000年鳥取県西部地震

Abstract

2000年10月6目に鳥取県西部を中心とするマグニチュード7.3の地震が発生した。震源域では10年以上前から断続的に地震活動が続いていた。本震による比較的大きな破壊領域は、この前駆的地震活動域を取り囲むように分布している。また余震活動は大きな破壊領域では少なく、逆に北西部のやや小さな破壊域で多く発生している。本震の直下では比抵抗の低い領域が存在すること、また直下30km付近には深部低周波地震が発生していたことがわかりこの地震発生に高温流体が関与した可能性も指摘された。

The earthquake with Mj 7.3 occurred in the western part of Tottori prefecture.At epicentral area, the higher level of intensity 6 were recorded. No one was killed, but more than 100 peoples were injured.The seismicity has been high on the border area of Tottori-Shimane prefecture. In the epicentral area, the swarm earthquakes have been occurred from 1989.Most of these swarm earthquakes distribute on the low slip portion of the main shock.Four low frequency earthquake which occurred at 30 km depth were observed after October 1997. About 12 hours before the main shock, small event of Ml .7 occurred at 3 km distance from the rupture start point of the main shock.Aftershock distribution was obtained from the routine network and the urgent temporary observations.On the south part, aftershocks distribute within the narrow zone, but they disperse in the north part. The induced earthquake occurred in two area where ware south-east of Mt. Daisenand east of Shimane prefecture. Most of aftershocks related with the rupture of main shock distribute on the low slip portion of the main shock.