CRUSTAL DEFORMATION PRECURSOR AND ITS STRAIN MAGNITUDE TRANSFORM

This paper has summarized 60 examples of short term and imminent precursors of crustal deformation of 13 moderately strong and larger earthquakes occurred in North China area since 1995. By statis tics of qualitative relation between short term and imminent anomaKes of crustal deformation and earthquakes, it is found that the anomalies at stations further away from the epicenter occurred earlier, the anomalies nearer to the epicenter occurred later, and the magnitude of earthquakes is directly proportion al to the space distribution of the anomalies. The anomalous shapes of displacement deformation across faults are divided into two types: one type is a tendency anomalous variation, another is a high frequency fluctuation. In this paper, a method has been proposed that the continuous deformati0n is trans formedto strain. From the examples 0f the Datong-Yanggao M6.1 earthquake on October 16, 1989 and the Datong-Yanggao M5-8 earthquake on March 26, 1991, it can be seen that earthquakes of ten occur near the high strain areas, the anomalous quantity can reach 10-6.