一种震荡型震磁效应的可能机制-膨胀硬化致稳、流体扩散失稳震磁效应

A POSSIBLE MECHANISM OF THE OSCILLATORY SEISMOMAGNETIC EFFECT-DILATENT HARDENING-STABILIZING, FLUID DEFUSING INSTABILIZING SEISMOMAGNETIC MODEL

摘要:

本文根据一些地震前后地磁场出现上下波动形态的震磁效应现象,以包体模式为基础,提出了该类震磁效应的可能的物理机制。
当包体处于临界失稳状态时,由于大量微裂隙的产生,使孔隙压力下降,岩石有效应力增加,导致包体硬化致稳;若周围有流体渗入包体,则将导致孔隙压力回升,有效应力下降,包体将再度失稳,然后又是致稳,直至最后由于包体动态失稳而发生地震。根据流体扩散磁效应理论,这个过程将引起上下波动型的震磁变化。
最后讨论了各种条件下该类震磁效应的可能形态,并指出这种韵律性的前兆现象可能有一定的普遍性,是短临地震预报中值得重视的一个现象。

Abstract:

One type of the seismomagnetic effects is represented,——oscillatory geomaglletic abnormality before some earthquakes. Based on the inclusion model a possible physical mechanism of above seismomagnetic effect is represented as well.
When the inclusion is in instable stage there are lots of microcracks in it, if there are fluid surrounding the inclusion, dilatancy that occurs more rapidly than fluid can diffuse into the newly created pore space, which can reduce the pore fluid pressure. A decrease of pore fluid pressure increases the effective compressive stress, and the inclusion will be hardening when fluid diffuses from surrounding material into the inclusion, the pore fluid pressure increases total compressive stress decreases, and the inclusion is weakened and is instability again. According to the theory of fluid diffusion of magnetic effect, the oscillatory seismomagnetic effect will cause this process. Finally, the reasons of different types of oscillatory seismo magnetic effect are discussed.