唐山地震部分强余震前的余震破裂特征

FRACTURE FEATURES OF AFTERSHOCKS OCCURRED BEFORE SOME STRONG AFTERSHOCKS OF TANGSHAN EARTHQUAKE

运用方向性函数研究了唐山地震的几个强余震前后发生在强余震震中附近的地震破裂特征。结果表明，强余震前发生的地震较强余震后发生的地震更倾向于单侧破裂，主破裂方向一般不指向未来强余震震中，而部分临近强余震前的小震破裂方向指向未来强余震震中，并对此作了物理解释。

篒n this paPer, the authors studied the fracture features of some after shocks nearthe epicenters around the strong aftershocks of Tangshan earthquake by using thedirectional function. It is found that the earthquakes before the strong aftershocks showmore clear tendency of unilateral fracture than those after thestrong aftershocks, andthe directions of principal fractures generally do not point to the epicenters of the futurestrong aftershocks. It is also found that the rupture directions of some earthquakesshortly before strong aftershocks point to the epicenters of the future strongaftershocks. Finally the authors explained those phenomena from the viewpoint of phys-ics.