论日本海区深震等深线凸进方向的动态变化及其在地震预报中的意义

THE DYNAM[C CHANGE OF THE PEAK DIRECTION OF ISOBATHS OF DEEP FOCUS EARTHQUAKES IN THE JAPAN SEA AND ITS SIGNIFICANCE IN EARTHQUAKE PREDICTION

深震等深线加深的梯度方向,反映了板块插入方向和板块俯冲力作用的主体方向;等深线凸进方向的动态变化,反映了贝尼奥夫带的偏转;日本海深源地震和我国东部地区浅震的个体(强震)和群体迁移,反映了深、浅部应力场强区的转移。这种转移的深层原因,可能与上地幔物质流流动方向变化有关。强区范围的圈定和转移规律,对地震的地点预报,具有重要意义。

The author has studied the general configuration of the isobaths map of deep focus earthquakes and its dynamic change in different periods since 1900.In the Japan Sea, change of the peak direction of isobaths of deep focus earthquakes was found in this area; a concept that the line of peak direction represents the main direction of subduction of the Pacific plate was put forward. The change of the directional line reflects the deflection of Benioff zone, resulting probably from the directional change of the stress field which was related to the variation of the flow direction of ma erials from the, upper mantle. Using this new idea, areas of stronger stress field in different periods in the eastern part of China are delineated, and the study on corresponding migrating regularity between deep and shallow earthquakes(group and single) with the deflection of the directional line is made. Finally the author proposes that the earthquake will continually remain cahn in the eastern part of china.