Numerical simulation of seismo-electromagnetic fields associated with a fault in a porous medium
Numerical simulation of seismo-electromagnetic fields associated with a fault in a porous medium
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DOI：
10.1093/gji/ggw144
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发表时间：
2016-07
影响因子：
2.8
通讯作者：
H. Ren;Qinghua Huang;Xiaofei Chen
中科院分区：
文献类型：
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作者：
H. Ren;Qinghua Huang;Xiaofei Chen
在这项工作中，我们进行了数值模拟的地震电磁场与断层在多孔介质中考虑电动效应。除多孔材料外，所采用的分层模型还包括固体材料，其中动电效应被忽略。首先，对埋置在固体半空间下的多孔半空间中的双耦合点源产生的瞬逝波和直接辐射电磁波进行了灵敏度研究。结果表明，瞬逝波和直接辐射电磁波都对介质的某些性质敏感，如孔隙度、盐度、流体粘度和固体层的电导率。然后，采用八层半空间模型，模拟了有限断层破裂过程产生的地震波和电磁波场。结果表明，动电效应是能够产生可观的corrupture电磁信号，但可观测性取决于一些因素，如震中距离，介质的属性，在故障所在的，和当地的活动水平的EM噪声。时间同步同震电磁信号是当接收器接近地下水位但位于固体介质中时记录的。除了震后电场外，我们的结果还显示了震后磁场，这在以前的动电效应模拟研究中还没有发现。震后磁场的产生可能需要足够强的介质非均匀性或流体压力梯度。
In this work, we carry out numerical simulations of the seismo-electromagnetic fields associated with a fault in a porous medium by considering the electrokinetic effect. In addition to porous materials, the adopted layered models comprise solid materials in which the electrokinetic effect is inoperative. First, sensitivity study is performed for the evanescent and direct radiation electromagnetic (EM) waves generated by a double couple point source embedded in a porous half-space below a solid half-space. Results suggest that both the evanescent and direct radiation EM waves are sensitive to some medium properties, for example porosity, salinity, fluid viscosity, and conductivity of solid layer. Then, adopting an eight-layer half-space model, we simulate the seismic and EM wavefields generated by the rupture process of a finite fault. It is shown that the electrokinetic effect is able to generate observable corupture EM signals, but the observability depends on some factors such as the epicentral distance, properties of the medium where the fault is located, and local activity levels of EM noise. Time synchronization coseismic EM signals are recorded when the receiver is close to the ground water level but located in a solid medium. In addition to the post-seismic electric field, our results also show the post-seismic magnetic field which has not been identified in previous simulation studies on the electrokinetic effect. The generation of the post-seismic magnetic field probably requires a sufficiently strong medium heterogeneity or fluid-pressure gradient.