| In the practice of geoelectric field observation,the traditional view is that the geoelectric field on the same site has the characteristics of uniformity.Therefore,between long polar distance and short polar distance in the same direction of the same field,the geoelectric field should have a high correlation,and this correlation is relatively stable.Based on long-term geoelectric field minute data of more than 50 geoelectric field stations nearby 13 typical earthquakes in different regions of mainland China in recent years,the paper systematically studied the correlation of the geoelectric fields at these sites and found:（1）During the tectonic activity is relatively quiet period,the correlation coefficient of the geoelectric field(δxy)between different azimuths of the same site or the correlation coefficient(δxx)between different polar distances in the same azimuth have relative stability;（2）during the occurrence of moderate-strong earthquakes δxy and δxx will decrease significantly in multitudinous sites near the epicenter,and the relative amplitude m of the decrease will not be less than 200%;（3）earthquakes mostly occur in the period where δxy and δxx decrease to the lowest level in each site;（4）this correlation decline phenomenon is directional and quasi-synchronous in time,gradually disappears with increasing epicentral distance.This study found that the changes in the correlation coefficients of the geoelectric field δxy and δxx are closely related to the occurrence of earthquakes.The significant decrease in δxy and δxx before and after the earthquake indicates that the geoelectric field of the site has a non-uniform variation during this period,which provides a new and tryable physical parameter for the identification of earthquake precursor information. |
