芦山7.0级地震前后岩石圈磁场异常变化研究*
倪 喆1,陈双贵2,袁洁浩3,伊 炜1,王 粲3

(1.云南省地震局,云南 昆明 650224; 2.甘肃省地震局,甘肃 兰州 73000; 3.中国地震局地球物理研究所,北京 100081)

地磁测量; 岩石圈磁场; 芦山地震; 龙门山断裂

Research on Anomalies Variation of Lithosphere Magnetic Field Before and After Lushan MS7.0 Earthquake
NI Zhe1,CHEN Shuang-gui2,YUAN Jie-hao3,YI Wei1,WANG Can3

(1.Earthquake Administration of Yunnan Province,Kunming 650224,Yunnan,China)(2. Earthquake Administration of Gansu Province,Lanzhou 730000,Gansu,China)(3. Institute of Geophysics,CEA,Beijing 100081,China)

geomagnetic measuring; lithosphere magnetic field; Lushan MS7.0 earthquake; Longmenshan Fault

备注

利用2011～2013年南北地震带104个地磁测点3期流动地磁矢量测量的可靠资料,获得了2期该区域岩石圈磁场的动态变化。分析了2013年4月20日四川芦山7.0级地震前后岩石圈局部磁场的动态变化特征,研究这种演化特征与该地震的关系。结果 表明:(1)地震前岩石圈磁场各要素均表现出异常特征,震后异常消失;(2)孕震过程中所产生的地震地磁异常空间大致以震中为圆心,半径约125 km;(3)孕震过程中垂直矢量的方向与龙门山断裂的构造运动呈反向,其矢量值在发震地点附近最小,这可能与该地震的类型为纯逆冲型有关。

Using the 3-term flow geomagnetic vector data recorded by 104 geomagnetic measuring sites in the north-south seismic belt during 2010 and 2013,we obtained the dynamic variation of the 2-term lithosphere magnetic,and analyzed the dynamic variation characteristics of the lithosphere local magnetic field before and after Lushan MS7.0 earthquake on Apr.20,2013 in Sichuan to research its relationship with the earthquake. The results showed that:(1)Anomalous characteristics was appeared in the magnetic elements of the lithosphere magnetic field before Lushan MS7.0 earthquake and disappeared after the earthquake;(2)The anomalous space distribution of the horizontal vector before the earthquake showed that the space of geomagnetic anomaly is in the range of 125 km from the epicenters in the process of earthquake preparation.(3)The direction of the vertical vector and tectonic movement of Longmenshan Fault were opposite in the process of earthquake preparation,and vertical vector value is minimum nearby the epicenter,which might be related to the Lushan MS7.0 earthquake of pure thrust type.