Localization and coalescence of seismicity before large earthquakes
Localization and coalescence of seismicity before large earthquakes
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DOI：
10.1093/gji/ggaa315
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发表时间：
2020-10-01
影响因子：
2.8
通讯作者：
Zaliapin, Ilya
中科院分区：
文献类型：
--
作者：
Ben-Zion, Yehuda;Zaliapin, Ilya
我们研究本地化过程中的低震级地震活动的发生与大地震使用三个互补的分析：（i）估计生产的岩石破坏的背景事件，（ii）不断变化的背景地震活动所占的分数面积和（iii）逐步合并成集群的个别地震。不同的技术提供了不同时间尺度和削弱受损区域空间范围的信息。技术（一）和（二）使用去聚类目录，以避免偶尔强烈的波动与余震序列，而技术（三）检查整个目录数据的发展集群。我们主要分析被锁定在地震间隔期的大断层周围的地震，并检查作为对比的例子，从蠕动的Parkfield部分的圣安德烈亚斯断层的地震活动。分析（i）的结果表明，1992年Landers地震、1999年Hector Mine地震、2010年El Mayor-Cucapah地震和2019年里奇克雷斯特地震在南加州和下加利福尼亚的主震之前的几十年里，在最终破裂带周围产生了岩石损伤。分析（ii）揭示了在这些主震和1999年土耳其杜兹采7级以上地震前2-3年的局部化（减少的分数面积）。技术（iii）的结果表明，个别事件往往迅速合并成集群在最后1-2年前的主震。对帕克菲尔德地区数据的相应分析表明，2004年6级地震前出现了相反的离域模式和聚集性下降。继续研究这些技术，再加上对大地测量数据的分析以及从实验室实验和模型模拟中获得的见解，可能会提高跟踪导致大地震的准备过程的能力。
We examine localization processes of low magnitude seismicity in relation to the occurrence of large earthquakes using three complementary analyses: (i) estimated production of rock damage by background events, (ii) evolving occupied fractional area of background seismicity and (iii) progressive coalescence of individual earthquakes into clusters. The different techniques provide information on different time scales and on the spatial extent of weakened damaged regions. Techniques (i) and (ii) use declustered catalogues to avoid the occasional strong fluctuations associated with aftershock sequences, while technique (iii) examines developing clusters in entire catalogue data. We analyse primarily earthquakes around large faults that are locked in the interseismic periods, and examine also as a contrasting example seismicity from the creeping Parkfield section of the San Andreas fault. Results of analysis (i) show that the M > 7 Landers 1992, Hector Mine 1999, El Mayor-Cucapah 2010 and Ridgecrest 2019 main shocks in Southern and Baja California were preceded in the previous decades by generation of rock damage around the eventual rupture zones. Analysis (ii) reveals localization (reduced fractional area) 2-3 yr before these main shocks and before the M > 7 Duzce 1999 earthquake in Turkey. Results with technique (iii) indicate that individual events tend to coalesce rapidly to clusters in the final 1-2 yr before the main shocks. Corresponding analyses of data from the Parkfield region show opposite delocalization patterns and decreasing clustering before the 2004 M6 earthquake. Continuing studies with these techniques, combined with analysis of geodetic data and insights from laboratory experiments and model simulations, might improve the ability to track preparation processes leading to large earthquakes.