Detection of deep low-frequency earthquakes in the Nankai subduction zone over 11 years using a matched filter technique
Detection of deep low-frequency earthquakes in the Nankai subduction zone over 11 years using a matched filter technique
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使用匹配滤波技术检测南开俯冲带 11 年来的深部低频地震
DOI：
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
S. Nakagawa
中科院分区：
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作者：
A. Kato;S. Nakagawa
为了提高我们对南海俯冲带地震带沿着低频地震（LFEs）长期行为的理解，我们将匹配滤波技术应用于2004年4月至2015年8月11年窗口期间密集和高灵敏度地震台网记录的连续地震数据。我们总共检测到约510，000个LFE，或约23倍于同期JMA目录中的LFE数量。在丰后海峡的长期缓慢滑动事件（SSE）期间，沿着断层走向间歇性地发生了一系列迁移性LFE爆发，震源传播缓慢。长期SSE释放的弹性能量似乎控制LFE活动的程度。我们在重大幕式地震和滑动（ETS）事件期间识别出缓慢迁移的LFE锋面，这些锋面延伸距离长达100 km，遵循扩散系数约为104 m 2 /s的扩散样空间演化模式。这种迁移模式密切匹配的时空演变的构造地震的研究报告。在较短的距离，高达15公里，我们发现了快速扩散的LFEs迁移的系数为~ 105 m2/s。我们还认识到，在主要的ETS事件中，LFE的快速迁移间歇性地发生在许多条纹中。这些观测结果表明，慢滑瞬变包含大量的较小的，时间上聚集的断层滑动事件，其演变是由扩散过程控制的。
To improve our understanding of the long-term behavior of low-frequency earthquakes (LFEs) along the tremor belt of the Nankai subduction zone, we applied a matched filter technique to continuous seismic data recorded by a dense and highly sensitive seismic network over an 11-year window, April 2004 to August 2015. We detected a total of ~ 510,000 LFEs, or ~ 23 × the number of LFEs in the JMA catalog for the same period. During long-term slow slip events (SSEs) in the Bungo Channel, a series of migrating LFE bursts intermittently occurred along the fault-strike direction, with slow hypocenter propagation. Elastic energy released by long-term SSEs appears to control the extent of LFE activity. We identify slowly migrating fronts of LFEs during major episodic tremor and slip (ETS) events, which extend over distances of up to 100 km and follow diffusion-like patterns of spatial evolution with a diffusion coefficient of ~ 10 4 m 2 /s. This migration pattern closely matches the spatio-temporal evolution of tectonic tremors reported by previous studies. At shorter distances, up to 15 km, we discovered rapid diffusion-like migration of LFEs with a coefficient of ~ 10 5 m 2 /s. We also recognize that rapid migration of LFEs occurred intermittently in many streaks during major ETS episodes. These observations suggest that slow slip transients contain a multitude of smaller, temporally clustered fault slip events whose evolution is controlled by a diffusional process.