老虎山断裂带大地电磁地震监测研究

Magnetotelluric Monitoring of Earthquakes in the Laohushan Fault Zone,Gansu Province

本文分析研究了2004年10月至2006年9月在老虎山断裂带附近一测点的5次大地电磁重复观测资料。观测期间在其断裂带的近距测点十数公里处,发生了最大震级为ML4.6的一组3级以上地震。揭示出了由大地电磁法观测到该地震活动过程所显示的深部电性变化的前兆特征,表明在震源区一相应深度范围在地震孕育过程中介质电阻率出现下降—上升—发震的变化过程。

In this paper, five repeated magnetotelluric sounding data at the Laohushan Fault Zone, Gansu province from Oct of 2004 to Sep of 2006 have been analyzed. In this period, a set of M〉3.0 earthquakes occurred in the fault zone, with the largest ME4. 6 about 10 km from the fault. The results indicate that the method of magnetotelluric sound- ing can observe the premonitory change of deep electric structure caused by seismic activity. The earthquake preparation process causes the resistivity of medium to drop, rise in the epicentral area and then earthquake occurs in the corresponding depth.