Abstract: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.
LI Yuan,LIU Xikang,ZHENG Zhijiang et al. Comprehensive Extraction of Fault Deformation Anomalies in Gansu and Nearby Areas and Summary of Earthquake Cases[J]. jgg, 2019, 39(12): 1254-1260.