Lower Mantle Seismicity Following the 2015 Mw 7.9 Bonin Islands Deep‐Focus Earthquake
Lower Mantle Seismicity Following the 2015 Mw 7.9 Bonin Islands Deep‐Focus Earthquake
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DOI：
10.1029/2021gl093111
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发表时间：
2021-07
影响因子：
5.2
通讯作者：
E. Kiser;H. Kehoe;Min Chen;Amanda Hughes-
中科院分区：
文献类型：
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作者：
E. Kiser;H. Kehoe;Min Chen;Amanda Hughes-
深源地震提供了深入了解俯冲板块如何在一系列空间和时间尺度上变形，因为它们下降到地幔。本研究使用4D震源成像方法来确定2015年小笠原群岛MW 7.9深源地震及其余震序列的质心位置。主震的震源成像显示出一个复杂的破裂，但与一个亚水平破裂面相一致。以前未被发现的早期余震被成像到大约750公里的深度，代表了第一次报告的下地幔开始的地震。这些事件和先前报道的一组较浅的远源余震发生在成像板段的上下边界，该板段在穿透下地幔时变形。我们假设主震失败允许重力沉降的板段发生产生的远余震序列。
Deep‐focus earthquakes provide insight into how subducting slabs deform over a range of spatial and temporal scales as they descend into the mantle. This study uses a 4D source imaging approach to determine centroid locations of the 2015 Mw 7.9 Bonin Islands deep‐focus earthquake and its aftershock sequence. Imaged sources of the mainshock show a complex rupture, but one that is compatible with a sub‐horizontal rupture plane. Previously undetected early aftershocks are imaged down to depths of approximately 750 km and represent the first reported earthquakes that initiate in the lower mantle. These events and a previously reported group of shallower distal aftershocks occur at the lower and upper boundaries of an imaged slab segment that deforms as it penetrates into the lower mantle. We hypothesize that mainshock failure allowed gravitational settling of the slab segment to occur which produced the distal aftershock sequences.