Electrical conductive fluid-rich zones and their influence on the earthquake initiation, growth, and arrest processes: observations from the 2016 Kumamoto earthquake sequence, Kyushu Island, Japan
Electrical conductive fluid-rich zones and their influence on the earthquake initiation, growth, and arrest processes: observations from the 2016 Kumamoto earthquake sequence, Kyushu Island, Japan
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DOI：
10.1186/s40623-020-01340-w
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发表时间：
2021-01-07
影响因子：
3
通讯作者：
Shimizu, Hiroshi
中科院分区：
文献类型：
--
作者：
Aizawa, Koki;Takakura, Shinichi;Shimizu, Hiroshi
地壳地震破裂往往在富含流体的区域附近开始。然而，它是相对未知的富流体区是否可以进一步促进或阻止这些破裂。我们利用200个站点的宽带大地电磁数据对2016年熊本地震序列震源区周围的电阻率结构进行成像，并讨论其与地震发生、增长和停止过程的定量关系。沿低电阻率富流体区（< 30 Ω m）外缘沿着发生的破裂倾向于成为大地震，而在富流体区远端或内部发生的破裂则不会。破裂被高温（> 400摄氏度）富流体区阻止，而较浅的低温（200-400摄氏度）富流体区促进或阻止破裂。这些结果表明，中地壳流体的分布有助于地壳地震的启动，增长和逮捕。破裂前孔隙流体的压力/温度梯度（空间差异）可能有助于破裂的开始、扩展和停止。
Crustal earthquake ruptures tend to initiate near fluid-rich zones. However, it is relatively unknown whether fluid-rich zones can further promote or arrest these ruptures. We image the electrical resistivity structure around the focal area of the 2016 Kumamoto earthquake sequence by using 200 sites broadband magnetotelluric data, and discuss its quantitative relationship to earthquake initiation, growth, and arrest processes. The ruptures that initiated along the outer edge of the low-resistivity fluid-rich zones (< 30 omega m) tended to become large earthquakes, whereas those that initiated either distal to or within the fluid-rich zones did not. The ruptures were arrested by high-temperature (> 400 degrees C) fluid-rich zones, whereas shallower low-temperature (200-400 degrees C) fluid-rich zones either promoted or arrested the ruptures. These results suggest that the distribution of mid-crustal fluids contributes to the initiation, growth, and arrest of crustal earthquakes. The pre-failure pressure/temperature gradient (spatial difference) of the pore fluids may contribute to the rupture initiation, propagation, and arrest.