Analysis of seismic geophysical anomalies before three earthquakes with MS≥4 in Shijiazhuang from 2014 to 2018
Six earthquakes with MS ≥ 4 occurred in Hebei Province from 2014 to 2018.The data anomalies recorded by the Shijiazhuang geophysical station network before the earthquakes were systematically analyzed,and we concluded that:①The data anomalies recorded at the Huanghua Well and Hejian Well before the Zhuolu MS 4.8 earthquake on September 6,2014,the Changli MS 4.3 earthquake on September 14,2015,and the Tangshan MS 4.2 earthquake on September 10,2016 were confirmed as geophysical anomalies;②The abnormal changes of water level in Huanghua Well and Hejian Well are synchronized with one or more large ascending step changes before the earthquakes,and the earthquakes occurred 2 to 3 months after recovering tonormal;③After analyzing the mechanisms of abnormal change of water level,we believe that the main reasons for recording pre-earthquake anomalies are non-uniformity of geological structure and high sensitivity of water level observation in the regions of Huanghua Well and Hejian Well.During earthquake preparation,the slight changes in stress and strain of seismogenic rock mass propagate to the aquifer of the observation well through the fracture zone,causing changes in the porosity of the aquifer rock mass.This yields in water exchange between the wellbore and the aquifer.Due to the good water conduction performance of the borehole and aquifer system of these two wells,the micro-strain of crustal rock mass is amplified,so the water level has a large step change before the earthquakes;④A time-axis comparison between the M-t map of earthquakes with MS≥3 and the frequency of unknown signals (times/month) shows that when unexplained data anomalies are frequently recorded for 4 consecutive months,there would be a multi-seismic period.
Shijiazhuang geophysical station networkdata tracking and analysisunexplained eventsgeophysical anomaly
万方数据
维普
