强震前地磁日变化感应电流线状集中分布孕震机理研究

Study on the Linear Concentrated Distribution Mechanism of Induced Current in Geomagnetic Diurnal Variation Before Strong Earthquakes

本文研究了地磁日变化感应电流的短期原地重现异常(简称重叠异常)与两次强地震前重力变化的关系,结果显示,两次强震前都出现感应电流重叠异常,在异常后半年内,重叠段端部附近区域出现重力负异常,其后发生地震。感应电流的重叠段与上地幔和壳内高导带走向基本一致,线状集中分布的地磁日变化感应电流的量级达数千安培,推测其孕震机理可能是某种因素导致上地幔和地壳内高导带出现"裂纹",深部流体进入"裂纹"形成"短时间高导通道",当"短时间高导通道"持续多天,或短期内原地不同日期出现"短时间高导通道"后,出现重叠异常,感应电流在重叠段端部高阻区产生热量,介质的热膨胀导致其上方地面发生变形,引起重力下降,并导致地壳水平挤压高应力处断层间摩擦阻力变小,发生地震。

The relationship between the short-term recurrence anomaly of the induced current of the daily variation of the geomagnetic vertical component(the overlapping anomaly)and the gravity change before two earthquakes is studied.It is found that within half a year after the occurrence of the anomaly,negative gravity anomalies appear near the end of the overlap segment.The direction of the overlapped section of induced current is consistent with that of the high conductivity zone in the upper mantle and crust and the induced current may several thousand amperes.We infer as follows.Some unknown factors lead to"cracks"in the upper mantle and crust,and the deep fluid enters into the"cracks"to form"short-time high conductivity channels".When the"channels"last for many days,or appear on different days in the same place in a short time,the induced current generates heat in the high resistance area at the end of the overlap section.The thermal expansion of the medium leads to the deformation of the ground above and results in the gravity drop.The horizontal compression of the crust leads to the reduction of the friction resistance between faults at the high stress area and then earthquakes occur.