甘肃及附近地区断层形变异常特征的综合提取与震例总结

基于20世纪80年代以来的跨断层短水准资料，利用“点-线-面”相结合的研究方法，全面分析甘肃地区1990~2016年8次5.5级以上地震的震前应变背景、断层活动和短期形变异常的时空演化特征。结果显示，多个地震震前不同层面上出现如下典型的异常特征：1）地震往往发生在垂直形变累积率的高值区或差异显著的高梯度带上，震前出现有序的形变场分布；2）震前不同断裂带之间或断裂带的不同段之间常存在显著的运动差异，发震断裂震前中短期运动速率显著增强，造成区域运动的不均衡；3）随着强震的逼近，显著异常场地在空间分布上明显向近震区迁移和集中，或近震源区的一些跨断层场地异常强度逐渐增大。地震震前典型异常的时、空、强演化特征说明，断层运动失稳前，近震区附近断层活动、应力应变场均有一定程度的显现，地震发生前断层活动存在不同往常的失稳波动现象，应力出现向近震源区传递的特征。

Comprehensive Extraction of Fault Deformation Anomalies in Gansu and Nearby Areas and Summary of Earthquake Cases

Based on short cross-fault level data from Gansu province since the 1980 s, using the research method of “point-line-surface”, the spatial and temporal evolution characteristics of strain background, fault activity and short-term deformation anomalies before 8 earthquakes of magnitude 5.5 or above from 1990 to 2016 are comprehensively analyzed. The results show that the following typical abnormal characteristics appear on different levels before multiple earthquakes:1) Earthquakes usually occur in the high value area or the high gradient zones of vertical deformation accumulation rate, and the orderly distribution of deformation field occurs before the earthquake; 2) There is often significant difference in motion between different faults or between different segments of fault zones before earthquakes, and the medium-term motion rates in seismogenic faults are significantly enhanced, resulting in imbalance of regional motion; 3) With the approach of the strong earthquake, significantly abnormal sites in the spatial distribution obviously migrate to, and concentrate at, the near seismic region, and abnormal intensity gradually increases in some cross-fault sites near the seismic source region. The time, space and intensity evolution characteristics of these typical anomalies before the earthquake indicate that fault activity and stress field near the earthquake zone have some representation before the fault movement instability, fault activity before the earthquake has different instability fluctuations, and the stress appears to transfer to the near source area.