华北地区强震前断层形变异常与演化特征

利用华北北部地区20世纪70年代以来的跨断层形变观测资料，研究了该区强震前的断层形变异常。结果表明：唐山、大同和张北地震前断层形变的中、短期前兆异常显著，说明剧烈的断层活动是强震发生的重要信息；唐山地震在形变异常恢复后或在恢复过程中发生的异常测项的比例高于大同和张北地震；断层活动存在10年左右周期的群体准同步阶段性特征；在大同和张北地震活跃期内，震前断层形变主要表现为突跳性(无趋势积累)短期异常，而在唐山地震活跃期内，断层形变主要表现为趋势性积累，这可能是华北6级～7级以上强震前断层形变异常特征的主要区别之一。

FAULT DEFORMATION ANOMALY AND ITS EVOLUTIONARY CHARACTER BEFORE STRONG EARTHQUAKES IN NORTH CHINA

In this paper,the cross fault deformation in the north of North China since 1970s have been analyzed systematically.The results show as follows.The medium short term precursory anomalies of fault deformation before earthquakes in Tangshan,Datong and Zhangbei are obvious,which indicate that the badly faulting is a important message of occurrence of strong earthquakes.The proportion of occurrence of anomalous items during and after deformation anomaly recovery of Tangshan earthquake is bigger than those of Datong and Zhangbei earthquakes.There also is a periodic character of approximative ten years in fault activity,which is almost synchronous and in a group.The conformation of fault deformation anomaly is a saltation in active period in Datong and Zhangbei earthquakes,while it is with certain trend for Tangshan earthquake.This is perhaps one of the main distinctions of the anomalous fault deformation characteristics before strong earthquake of over 6 or over 7 in North China.