像力及其在震源过程中的作用

本文应用固体物理学中位错所受自由面的像力的概念来讨论调整单元(自由面或软弱介质)对孕震震源地区断层的蠕裂、临震前锁住段断层中预位移的传播以及地震发生时裂缝的失稳传播的影响。推导了几种不同形状的自由边界对螺型位错和刃型位错作用的像力的表达式。以直立倾滑断层为例求出了震源地方断层某一段发生相对位移时由于自由面的像力作用而在断层上引起的附加应力场。估算了实际断裂情况下此附加应力场的数量级。认为像力的作用在震源过程中尤其是在研究对大震的触发作用时是不可忽视的。从像力的观点出发解释了地震发生时的一些现象。

THE IMAGE FORCE AND ITS APPLICATION TO EARTHQUAKE SOURCE PROCESS

By applying the conception of image force acted on dislocation by free surface in solid physics,in this paper the following topics have been dis-cussed.the effects of adjustmentary elements on the creep fracture of the fault in earthquake source,the propagation of creep slip just before earth-quake in the locked fault and unsteady propagation of crack when earth-quake occurs.The formulas of the image force acted on screw and edge dislocations by sevral different shape free-boundaries have been derived.As an example,the additional stress field on the fault due to the image force of free surface when the relative displacement of a section of the fault in earthquake source occurs bas been calculated.The order of this additional stress field has been estimated under the actual condition.We come to the conclusion that the effects of image force can not be ignored in earthquake source process,particularly,in studying the trigger effects on large earthquake.Based on the point of image force,some phenomena following when the earthquake occurs have been interpreted.Studying the dynamic effects of image force would be helpful for catching some short-term and immediate precursors imformation.