Investigation of the characteristics of geoelectric field earthquake precursors: A case study of the pingliang observation station, China

Abstract

An increasing number of earthquake precursors have been observed by geoelectromagnetic stations; however, the statistical characteristics of the earthquake and geoelectric field (GEF) are not well known. Based on the sliding correlation method (SCM) and its validity test, we analyzed 125 months of continuous data from the Pingliang (PL) GEF station in China. Two factors, seismic energy and epicentral distance (D), were used to select the earthquake events. When the lower limit of the magnitude energy is set as 106 J/km2, the number of earthquake events in area A (D < 200 km) is 36, and the number of seismic events in area B (200 km ≤ D < 365 km) is 34. In the analysis of the calculated results, the mean value of 1000 times random test SCM calculation is taken as the anomaly standard. In addition, it is found that the anomalies occurring north-south, and north-east of PL station are the most significant in area A, and the anomalies are concentrated approximately 8-26 days before the earthquakes. There is no obvious correlation east-west of PL station in area A, and there is no similar abnormal phenomenon in area B. The reasons and probably mechanism of the investigation results are analyzed and discussed in combination with the fault belt features of the study area, numerical simulation, and laboratory rock fracturing experiments. The uniqueness of the results is verified by reducing the energy standard of a single earthquake. This investigation supports the statistical point of view of the microcosmic interpretation of GEF abnormalities, provides significant suggestions for the selection of electrode-layout orientations used for GEF observations and also provides a reference for the gathering of the seismic precursor information.