OBSERVING CRUSTAL MEDIA VARIATION IN LUANXIAN AREA BY USING REPEATED EARTHQUAKES

The earthquakes with M_L≥2.0 from January 2002 to August 2010 occurred in Luanxian area are relocated using the method of double difference, the locations of the repeated earthquakes in the study area are normalize by using ray-tracing method, and the P-wave travel time difference change of the repeated earthquakes are calculated after corrected with ray tracing method.The results show that before the Luanxian M_L5.0 earthquake in the January 20, 2004 and Luanxian M_L4.7 earthquake in the March 6, 2010, the low value abnormal change of P-wave travel time difference is found at selected seismic stations.