Characteristics of Frequent Dynamic Triggering of Microearthquakes in Southern California
Characteristics of Frequent Dynamic Triggering of Microearthquakes in Southern California
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DOI：
10.1029/2020jb020820
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发表时间：
2020-12
期刊：
影响因子：
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通讯作者：
W. Fan;A. Barbour;E. Cochran;G. Lin
中科院分区：
文献类型：
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作者：
W. Fan;A. Barbour;E. Cochran;G. Lin
据报道，地震的动态触发是在各种断层系统中发生的。触发的地震被认为是由通过的地震波引起的动态应力变化直接引起的，或者是由通过的波引发的其他非线性过程间接引起的。由于普遍缺乏高分辨率地震目录和定量评估触发响应（特别是延迟响应）的可靠方法，区分这些物理机制很困难。在这里，我们使用南加州的高分辨率地震模板匹配目录来系统地评估 2008 年至 2017 年圣哈辛托断层带和索尔顿海地热田的远震动态触发模式。我们开发了一种新的统计方法来识别触发案例，发现大约每 5 起全球 Mw ≥ 6 地震中就有 1 次动态触发南加州的微地震。触发响应包括瞬时触发和延迟触发，显示出高度异构的模式并指示可能不断变化的触发阈值。我们没有观察到可以区分触发地震和非触发事件的明确峰值地速触发阈值，但地震动的频率内容存在细微差异，可以区分地震。与背景地震活动的深度分布相反，已识别的触发地震往往集中在发震带的边缘。尽管瞬时触发的地震可能是动态库仑应力变化的结果，但延迟动态触发的情况最好用非线性触发过程来解释，包括循环材料疲劳、加速瞬态蠕变和随机摩擦不均匀性。
Dynamic triggering of earthquakes has been reported at various fault systems. The triggered earthquakes are thought to be caused either directly by dynamic stress changes due to the passing seismic waves, or indirectly by other nonlinear processes that are initiated by the passing waves. Distinguishing these physical mechanisms is difficult because of the general lack of high‐resolution earthquake catalogs and robust means to quantitatively evaluate triggering responses, particularly, delayed responses. Here we use the high‐resolution Quake Template Matching catalog in Southern California to systematically evaluate teleseismic dynamic triggering patterns in the San Jacinto Fault Zone and the Salton Sea Geothermal Field from 2008 to 2017. We develop a new statistical approach to identify triggered cases, finding that approximately 1 out of every 5 global Mw ≥ 6 earthquakes dynamically trigger microearthquakes in Southern California. The triggering responses include both instantaneous and delayed triggering, showing a highly heterogeneous pattern and indicating possible evolving triggering thresholds. We do not observe a clear peak ground velocity triggering threshold that can differentiate triggering earthquakes from nontriggering events, but there are subtle differences in the frequency content of the ground motion that may differentiate the earthquakes. In contrast to the depth distribution of background seismicity, the identified triggered earthquakes tend to concentrate at the edges of the seismogenic zones. Although instantaneously triggered earthquakes are likely a result of dynamic Coulomb stress changes, the cases of delayed‐dynamic triggering are best explained by nonlinear triggering processes, including cyclic material fatigue, accelerated transient creep, and stochastic frictional heterogeneities.