Detection of earthquake swarms at subduction zones globally: Insights into tectonic controls on swarm activity
Detection of earthquake swarms at subduction zones globally: Insights into tectonic controls on swarm activity
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DOI：
10.1002/2017jb014188
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发表时间：
2017-07
期刊：
影响因子：
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通讯作者：
T. Nishikawa;S. Ide
中科院分区：
文献类型：
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作者：
T. Nishikawa;S. Ide
地震群的特征是地震活动率增加，但没有明显的主震，也不遵守大森定律。在俯冲带，它们被认为与板块界面上的慢滑事件（SSEs）有关。因此，俯冲带中的地震群可以作为慢滑事件的潜在指标。然而，俯冲带地震群的全球分布仍不清楚。在这里，我们提出了一种方法来检测这样的地震序列使用时空流行型余震序列模型。我们将这种方法应用于1995-2009年期间在俯冲带记录的高级国家地震系统目录中的地震活动（M ≥ 4.5）。我们探测到453个星群，大约是以前星表中观测到的6.7倍。一些大地震的前震也被检测为震群。在某些俯冲带，例如日本的茨木-隐岐，震群状前震和普通震群在同一位置重复发生。鉴于前震和震群都与板块界面上的SSE有关，这些地区可能经历了反复出现的SSE。然后，我们比较了集团活动和俯冲带的构造性质，发现集团活动与俯冲前传入板块的曲率呈正相关。这一结果意味着，无论是由水化传入板或板的界面上的不均匀性，由于断裂板弯曲控制的群活动。
Earthquake swarms are characterized by an increase in seismicity rate that lacks a distinguished main shock and does not obey Omori's law. At subduction zones, they are thought to be related to slow‐slip events (SSEs) on the plate interface. Earthquake swarms in subduction zones can therefore be used as potential indicators of slow‐slip events. However, the global distribution of earthquake swarms at subduction zones remains unclear. Here we present a method for detecting such earthquake sequences using the space‐time epidemic‐type aftershock‐sequence model. We applied this method to seismicity (M ≥ 4.5) recorded in the Advanced National Seismic System catalog at subduction zones during the period of 1995–2009. We detected 453 swarms, which is about 6.7 times the number observed in a previous catalog. Foreshocks of some large earthquakes are also detected as earthquake swarms. In some subduction zones, such as at Ibaraki‐Oki, Japan, swarm‐like foreshocks and ordinary swarms repeatedly occur at the same location. Given that both foreshocks and swarms are related to SSEs on the plate interface, these regions may have experienced recurring SSEs. We then compare the swarm activity and tectonic properties of subduction zones, finding that swarm activity is positively correlated with curvature of the incoming plate before subduction. This result implies that swarm activity is controlled either by hydration of the incoming plate or by heterogeneity on the plate interface due to fracturing related to slab bending.