西太平洋Benioff带的形态及其应力状态

CHARACTERISTICS OF THE SUBDUCTION ZONE IN THE WESTERN PACIFIC AND ITS STRESS STATE

利用 1 970～ 1 998年的地震资料 ,研究了西太平洋Wadati Benioff带形态 ,发现各区域Wadati Benioff带的倾角与板块俯冲速度有关 ,俯冲速度越大 ,倾角越小 ;利用 1 976～ 2 0 0 2年哈佛大学的震源机制资料 ,对各区域地震断层类型进行了统计 ,结果表明 :地震断层类型也与俯冲速度有关 ,俯冲速度大的地区逆断层数量高达 74 %以上 ,俯冲速度小的地区正断层数量上升到 4 5 %左右 ;本文还探讨了西太平洋板块水平向运移的主动力方向 ,认为该方向为2 83°.

The distribution of earthquakes in the western Pacific is studied using the hypocenters determined by ISC. from 1970 to 1998. The result shows that the dip angles of the Benioff zone are correlated with velocity of the plate movement in different regions. The dip angles become smaller when the speed becomes larger. Focal mechanisms of events M b≥5.0 from 1976 to 2002 are analyzed using the data from Harvard university. It shows that types of faults are related with velocity of plate motion. In the area of higher velocity of plate motion, the number of thrust faults is more than 74% of the total. In the area of smaller one, the proportion of normal faults raises up to about 45%. The western Pacific horizontal movement dominants force direction, which is 283°.