THE REDETERMINATION OF HYPOCENTRAL LOCATION FOR PRESENT EARTHQUAKES IN HONGDONG AND LINFEN AREA,SHANXI PROVINCE

the hypocentral locations of 1670 medium and small earthquakes in Hongdong(M=8, 1303) and Linfen(M=7 3/4, 1695) areas are redetermined with the data recorded by Linfen wireless seismic network.The result shows that re determined results of forcal depths are much better than the old ones.The precision of hypocentral locations is improved.The dense area of present earthquakes in the region where the two historical strong earthquakes occurred is consistent respectively with the high intensity region of the two historical strong earthquakes in long axis' direction, shape and size.It reflects that present small earthquakes are restricted by focal faults of historical strong earthquakes.The distribution of focal depths of small earthquakes shows that focal faults of the two historical strong earthquakes should be shallow.It provides fine foundational ata for the study of focal fault of historical strong earthquakes with the group feature of present small earthquakes.