Abstract:
At a given site, the correlation coefficient
δxy between geoelectric field with different azimuths, or
δxx between geoelectric field with differernt polar distances for the same azimuth can express the complexity of site geoelectric field variation. This paper analyzed the geoelectric field correlation coefficient
δxy and
δxx based on the geoelectric field data from more than fifty sites around five typical earthquake epicenters. The results show that
δxy and
δxx of a site are relatively stable during a quiet period of seismic activity. During a moderate earthquake, the
δxy and
δxx for most of the sites near the epicenter decrease significantly. This phenomenon is directional and quasi-synchronous in time, and gradually disappears with epicentral distance increasing. Furthmore, in viewpoint of mechanism, it is deduced that the decrease in
δxy and
δxx reflects the non-uniformity of geoelectric field variation in the local sites near the epicenter.