A STUDY ON GROUP ANOMALIES OF SEISMIC ACTIVITY PARAMETERS BEFORE MODERATE EARTHQUAKES IN THE EASTERN SHANDONG AND ITS OFFSHORE AREAS

In this paper, the group anomalies of seismic activity parameters appeared before sixteen earthquakes of M_L≥4.7 in eastern Shandong and its offshore areas since 1970 are studied.The results show that seismic activity parameters related to seismic intensity and frequency are more sensitive to moderate earthquake.Generally, the values of Et, Qp and η are in low level or drop from high level before moderate earthquake, while the values of the other seismic parameters are in high level.Fourteen seismic activity parameters sensitive to moderate earthquake are selected from twenties, and the group abnormal indexes of which are determined.If more than ten parameters of the fourteens show abnormal, the area may be at the risk of occurring earthquake of M_L≥5.0.