Fault‐Valve Behavior Estimated From Intensive Foreshocks and Aftershocks of the 2017 M 5.3 Kagoshima Bay Earthquake Sequence, Kyushu, Southern Japan
Fault‐Valve Behavior Estimated From Intensive Foreshocks and Aftershocks of the 2017 M 5.3 Kagoshima Bay Earthquake Sequence, Kyushu, Southern Japan
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根据 2017 年日本南部九州鹿儿岛湾地震序列强烈前震和余震估计的断层阀行为
DOI：
10.1029/2020jb020278
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Hasegawa Akira
中科院分区：
文献类型：
--
作者：
Matsumoto Yoshiaki;Yoshida Keisuke;Matsuzawa Toru;Hasegawa Akira
确定地球内部的流体迁移和孔隙压力变化是了解地震发生的关键。我们研究了2017年日本南部九州鹿儿岛湾ML5.3地震的强烈前震和余震的时空特征，以研究控制该地震序列的物理过程。我们重新定位的震源显示前震在一个具有陡峭倾角的清晰平面上移动。主震破裂起始于前震空区边缘。前震空区的大小与由震源角频率估计的主震空区大小相当，表明前震空区对应于主震的大滑移区。余震沿沿着几个陡倾面向上迁移，其地震活动模式偏离了典型的主震-余震类型。这种地震活动图象的偏离以及震源的迁移表明，孔隙压力迁移和地震滑动等地震活动过程对这次地震序列有一定的影响。我们建立了以下假设。首先，来自俯冲板片的流体向上迁移并侵入断层面，降低了断层强度，导致前震序列和潜在的地震滑动。第二，主震破裂是由于断层强度降低，在强度相对较高的地区剪切应力增加。第三，孔隙压力增加与故障后流体排放引起的余震向上迁移。这些观测结果与断层阀模型相一致，表明了流体运动不仅在震群中而且在前震-主震-余震序列中的重要性。
Determining fluid migration and pore pressure change within the Earth is key to understand earthquake occurrences. We investigated the spatiotemporal characteristics of the intense foreshocks and aftershocks of the 2017 ML5.3 earthquake in Kagoshima Bay, Kyushu, southern Japan, to examine the physical processes governing this earthquake sequence. Our relocated hypocenters show the foreshocks moved on a sharply defined plane with a steep dip. The mainshock rupture initiated at the edge of the foreshock seismic gap. The size of the foreshock seismic gap is comparable to that of the mainshock estimated from the source corner frequency, suggesting this seismic gap corresponds to the large slip region of the mainshock. The aftershocks migrated upward along several steeply dipped planes with a seismicity pattern that deviated from the typical mainshock–aftershock type. This deviation of seismicity pattern, together with the hypocenter migrations, suggests aseismic processes, such as pore pressure migration and aseismic slip, affected this earthquake sequence. We established the following hypothesis. First, fluids originating from the subducting slab migrated upward and intruded into the fault plane, reducing the fault strength and causing the foreshock sequence and potentially aseismic slip. Second, the mainshock rupture occurred due to the decreased fault strength and the increased shear stress in an area with relatively high strength. Third, pore pressure increase associated with post‐failure fluid discharge caused the upward aftershock migration. These observations are consistent with the fault‐valve model and show the importance of fluid movement at depth not only in earthquake swarms but also in foreshock–mainshock–aftershock sequences.
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影响因子：
5.2
作者：
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DOI：
10.1002/2016jb013022
发表时间：
2016
期刊：
Journal of Geophysical Research: Solid Earth
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DOI：
--
发表时间：
2006
期刊：
AGU Monograph on Earthquakes : Radiated energy and the physics of earthquake faulting 170
影响因子：
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