Abstract:

Limited by  the distribution of stations, velocity structures and  the uncertainty of picking arrivals, the precision for the relocation of earthquakes is usually  not sufficient. We collected the data of arrival times recorded by the seismic networks and then used the double-difference method to relocate 1 400 earthquakes occurred in  Haicheng region（39°N-43°N，120°E-126°E）in the last 20 years. Comparing to the original results of the earthquake locations, the results obtained  by the double-difference method in this study  indicate that: 1) The earthquake distributions become more convergent, especially in the region between 40.5°N and 41.0°N and between 122.0°E and 123.0°E, and more consistent with the trend of the fault along the Haicheng-Dayang River; 2) Most of earthquakes occurred in the depth from 5 to 24 km, because there exists a low-velocity and high-conductivity zone in the crust; 3) From the cross sections, many earthquakes distribute as a shape of columnar  along the depth because there exists a comminuted fracture zone which extending from the surface to the depth of 25 km. The root-mean-square travel-time residual  reduces from 0.74 s to 0.26 s  after the relocation using the double-difference method. The study also  indicates that the magnitude is related to the number of earthquakes in this region. If the number of earthquakes increases abruptly, the  probability for the occurrence of a large earthquake increases as well.

Key words: double-difference relocation method, fault, earthquake prediction, Haicheng,Liaoning Province