Earthquake Swarm Detection Along the Hikurangi Trench, New Zealand: Insights Into the Relationship Between Seismicity and Slow Slip Events
Earthquake Swarm Detection Along the Hikurangi Trench, New Zealand: Insights Into the Relationship Between Seismicity and Slow Slip Events
复制标题
新西兰希库朗吉海沟沿线的地震群探测：深入了解地震活动与慢滑事件之间的关系
DOI：
10.1029/2020jb020618
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Okada Yutaro
中科院分区：
文献类型：
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作者：
Nishikawa Tomoaki;Nishimura Takuya;Okada Yutaro
地震群是指在没有明显主震的情况下，地震活动频率的异常增加，通常伴随着短暂的地震过程，如流体运移和沿断层的幕式地震滑动。对地震群活动的调查可以深入了解地震过程和地震活动性之间的因果关系。新西兰Hikurangi海沟沿板块界面的慢滑事件经常伴有强烈的地震群。然而，这些地震群的详细时空分布尚不清楚。本文利用流行型余震序列（ETAS）模型检测了沿Hikurangi海沟的地震群（M≥3），并建立了新的地震群目录（1997-2015）。我们将地震群目录与全球卫星导航系统（GNSS）的时间序列数据、现有的SSE和构造地震目录进行了比较。探测到的119次地震群序列多为板内事件，震中主要集中在北岛东海岸，而许多构造地震位于内陆。在探测到的地震群中，有25个发生在GNSS因已知或新探测到的地震而发生的瞬态向东位移前后的25天内。我们发现，地震群有时比GNSS位移早几天以上。因此，SSE诱发的应力加载并不是这些前SSE地震群的合理触发机制。我们认为，在SSE之前，板块内积聚的高流体压力可能导致了板块内流体的迁移，从而引发了SSE之前的地震群。
Earthquake swarms, which are anomalous increases in the seismicity rate without a distinguishable mainshock, often accompany transient aseismic processes, such as fluid migration and episodic aseismic slip along faults. Investigations of earthquake swarm activity can provide insights into the causal relationship between aseismic processes and seismicity. Slow slip events (SSEs) along the plate interface in the Hikurangi Trench, New Zealand, are often accompanied by intensive earthquake swarms. However, the detailed spatiotemporal distribution of these earthquake swarms is still unclear. Here, we use the epidemic‐type aftershock‐sequence (ETAS) model to detect earthquake swarms (M≥ 3) and create a new earthquake swarm catalog (1997–2015) along the Hikurangi Trench. We compare the earthquake swarm catalog with Global Navigation Satellite System (GNSS) time series data, and existing SSE and tectonic tremor catalogs. Most of the detected (119) earthquake swarm sequences were intraplate events, and their epicenters were mainly concentrated along the east coast of the North Island, whereas many tectonic tremors were located inland. Twenty‐five of the detected earthquake swarms occurred within 25 days before and after transient eastward GNSS displacements due to known or newly detected SSEs. We find that the earthquake swarms sometimes preceded the GNSS displacements by more than several days. SSE‐induced stress loading is therefore not a plausible triggering mechanism for these pre‐SSE earthquake swarms. We propose that high fluid pressure within the slab, which accumulated before the SSEs, may have caused intraplate fluid migration, which in turn triggered the pre‐SSE earthquake swarms.