论西安地裂缝

GROUND FISSURE IN THE CITY OF XI'AN

西安地裂缝具定向延伸、多级羽列和成带、等距的分布格局,为水平左旋和南盘依次下落的同步位错。是基底断裂在统一区域应力场作用下,长期蠕动形成的隐伏微细裂缝,在地下水活动的附加作用下显现出来的一系列构造地裂缝。其发生方式为多点双向破裂,发生时间和活动高峰依次由南向北迁移。它们不均匀地蠕滑、时隐时现,有4、20、400和750年四种活动周期,可与渭河盆地的地震活动对应,是区域构造应力场加强的信息。

The ground fissure in the City of Xi' an show leftlateral and are characterized by prevailing orientation, en echelon, roughly constant step-intervals and southern blocks relatively falling down. The fissures have originally been created sporadically by the regional stress field and consequently enlarged by the groundwater activity. Tha appearance of fissures seems earlier in the north and gradually migrates to the south. The slips along these fiasures are not uniform, but with quaci-peroods of 4,20,400 and 750 years respectively, which seemingly correlate with the periods of seismicity in the region. This indicates that the ground fissures and earthquakes both are under the control of the same regional stress.