Precursory Abnormal Characteristics of Geoelectric Field: A Case Study of Seismostation in 625 Research Institute of Aviation Industry Corporation of China

The geoelectric field data recorded for more than thirty years at seismostation in 625 Research Institute of Aviation Industry Corporation of China were analyzed, and eight sets of data including four sets of long-term abnormal signals and four sets of short-term abnormal signals were extracted. The abnormal short-term signals correspond to four M_s > 6.0 earthquakes. The geoelectric field signals have the following characteristics. (1) The long-term geoelectric field curves include precursory information from many earthquakes with different magnitudes and epicenter distances. The near-field and major earthquakes control the trendy of geoelectric field curves. Meanwhile big far earthquakes and small near earthquakes can cause oscillations up and down. (2) In the four short-term signals, we find that the geoelectric field curves show a common pattern of up(down), return, bound and occuring phases. The geoelectric field abnormal forms have similarity and repeatability. This proves that the geoelectric field observation can monitor the impending earthquake precursor. A new method to predict the occurrence-time is found. Based on the number of return days approximately be equal to the number of bound days, the date of occurrence time is the date of return plus the number of bound days. It pushes further the method of geoelectric field short-term earthquake precursor toward practice.