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 Ωm) 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 °C) fluid-rich zones, whereas shallower low-temperature (200–400 °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.

中文翻译：

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富含导电流体的区域及其对地震发生、增长和停止过程的影响：来自日本九州岛 2016 年熊本地震序列的观测结果

地壳地震破裂倾向于在富含流体的区域附近开始。然而，富流体区是否可以进一步促进或阻止这些破裂，还相对未知。我们使用 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 Ωm）外缘开始的破裂往往成为大地震，而在富流体区远端或内部开始的破裂则没有。高温（> 400 °C）富流体区阻止了破裂，而较浅的低温（200-400 °C）富流体区促进或阻止了破裂。这些结果表明中地壳流体的分布有助于地壳地震的发生、发展和停止。孔隙流体的破裂前压力/温度梯度（空间差异）可能有助于破裂的开始、扩展和停止。