一、引言四川是多震之地,但绝大多数是发生在地壳内的浅源地震。地震产生的地形、地质变化及各种物理、化学变化是地壳内断裂活动引起的。地震调查及震源参数说明:发震断裂面倾角一般都很陡立,震时以扭性或侧伏角很小的压扭性或张扭性活动为主,主压应力轴水平或近于水平。所以,可以近似地按水平应力场来分析四川 I. INTRODUCTION Sichuan is a place with many earthquakes, but the vast majority are shallow earthquakes that occur in the earth’s crust. The terrain, geological changes and various physical and chemical changes produced by earthquakes are caused by the fracture activity in the crust. Seismic survey and source parameter description: Seismic fault surface dip angle is generally very steep, earthquake with torsional or small lateral compression or torsional shear-based activities, the main compressive stress axis at or near the level. Therefore, we can analyze Sichuan by horizontal stress field