Comprehensive detection of very low frequency earthquakes off the Hokkaido and Tohoku Pacific coasts, Northeastern Japan.
Comprehensive detection of very low frequency earthquakes off the Hokkaido and Tohoku Pacific coasts, Northeastern Japan.
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综合探测日本东北部北海道和东北太平洋沿岸的甚低频地震。
DOI：
10.1029/2019jb017988
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Takuto Maeda
中科院分区：
文献类型：
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作者：
Satoru Baba;Akiko Takeo;Kazushige Obara;Takanori Matsuzawa;Takuto Maeda
甚低频地震（VLFEs）是慢地震的一种，发生在孕震区附近，可以作为板间慢滑动的替代。我们调查了北海道和东北太平洋沿岸的VLFE活动，太平洋板块在北美板块下俯冲。2003年1月至2018年7月期间，通过匹配滤波器技术，利用基于三维速度结构模型计算的合成波形，对VLFE进行了全面检测。2003年十胜冲地震（Mw 8.0）的余震活动与北海道沿海VLFE分布的时空一致性表明，VLFE活动可以反映板间的缓慢滑动。在2011年东北地震（Mw9.0）的大同震滑动区内，VLFE活动此后较低，而在该地区以外，VLFE活动在2011年东北地震后增加。这些特征与从重复地震中估计的无震滑动分布是一致的。VLFE有时被Mw为6-7的板间地震的余震激活，例如2008年的福岛-冲地震和2011年东北地震的余震。即使在特大地震同震滑动区，我们也发现在特大地震之间的一个震间期内，每隔3个月到1年就会发生一次幕式爆发。这样的VLFE爆发可能表明在地震间隔期间的小滑动。
Very low frequency earthquakes (VLFEs), classified as one type of slow earthquake, occur near seismogenic zones and can be a proxy for interplate slow slip. We investigated VLFE activity off the Hokkaido and Tohoku Pacific coasts, where the Pacific plate subducts under the North American plate. Comprehensive detection of VLFEs is performed for the period from January 2003 to July 2018 by a matched‐filter technique utilizing synthetic waveforms calculated based on a three‐dimensional velocity structure model. The spatiotemporal consistency between the afterslip of the 2003 Tokachi‐Oki earthquake (Mw 8.0) and VLFE distribution off the Hokkaido coast suggests that VLFE activity can reflect interplate slow slip. Inside a large coseismic slip area of the 2011 Tohoku earthquake (Mw 9.0), the VLFE activity was low thereafter, whereas outside the area, VLFE activity increased after the 2011 Tohoku earthquake. These characteristics are consistent with aseismic slip distributions estimated from repeating earthquakes. VLFEs were sometimes activated by afterslips of interplate earthquakes with Mw of 6–7, such as the 2008 Fukushima‐Oki earthquake and aftershocks of the 2011 Tohoku earthquake. Even in the coseismic slip areas of very large earthquakes, we found the occurrence of episodic bursts every 3 months to a year during an interseismic period between very large earthquakes. Such VLFE bursts may suggest small slips during the interseismic period.