2020年7月12日唐山MS5.1地震前通州台井下地电阻率变化

Apparent Resistivity Variations before Tangshan MS5.1 Earthquake on July 12,2020 Recorded at Tongzhou Station

摘要:

通州地震台井下地电阻率观测于2019年11月完成建设，完成相关测试后于2020年投入实际观测。在2020年7月12日河北唐山M_S5.1地震前，地电阻率呈现出一定的变化，约从4月上旬开始NE和NW测道同步出现下降变化，6月中旬开始NW测道出现转折回升。EW测道同期存在一定的上升变化，但变化幅度约为NE测道幅度的1/4。此次地震的震源机制解为走滑型，最大主压应力方位为101°，与NE、NW和EW测道的夹角分别为70°、50°和10°。震前NE测道下降幅度最大，NW测道次之，EW测道变化幅度最小，符合实验结果和地震前地电阻率各向异性变化特征。

Abstract:

The apparent resistivity well-observation of Tongzhou station was completed in November 2019,and has been put into practice observation in 2020 after relevant tests have been completed. Before the M_S5.1 earthquake in Tangshan,Hebei Province on July 12,2020 the apparent resistivity showed a certain degree of variations as early as in April,in which the NE and NW observations have been decreasing simultaneously,and the NW observation turned upward since mid-June. The EW observation has a certain rise in the same period,with the variation range is about 1/4 of the NE observation. The focal mechanism solution of this earthquake is strike-slip type. The direction of the maximum principal compressive stress(P axis)is 101°. The angle between the P axis and NE,NW and EW observation is 70°,50° and 10°,respectively. The NE observation dropped the most before the earthquake,followed by the NW observation,whereas the EW observation changed the least,which conforms to the experimental results and the practical observation of that the apparent resistivity anisotropic changes before earthquakes.