Spatiotemporal Distribution of Shallow Tremors Along the Nankai Trough, Southwest Japan, as Determined From Waveform Amplitudes and Cross‐Correlations
Spatiotemporal Distribution of Shallow Tremors Along the Nankai Trough, Southwest Japan, as Determined From Waveform Amplitudes and Cross‐Correlations
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根据波形幅度和互相关确定日本西南部南海海槽沿线浅层地震的时空分布
DOI：
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
A. Noda
中科院分区：
文献类型：
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作者：
K. Tamaribuchi;M. Ogiso;A. Noda
俯冲带中的浅源慢地震与大逆冲断层附近板块边界应力的时空变化有关。部署在日本西南部南海海槽孕震区的海底电缆地震仪（OBS）密集网络（DONET）实现了对地震的真实的实时监测。由于震颤信号的振幅非常低，即使被OBS记录，我们开发了一种混合方法，该方法同时使用基于互相关的走时和波形振幅来确定震颤震源。我们将我们的方法应用于2016年4月至2021年9月连续五年DONET记录期间观察到的波形，以检测超过6，500次震颤，包括2016年，2018年和2020-2021年的三次主要事件。每一幕的地震分布在两个区域，即纪伊半岛东南部和室户角外，沿海沟轴线沿着100 km以上的距离。我们还估计了地震能量率，发现对于三个主要的地震事件，能量率随着时间的推移逐渐增加。2018年和2020-2021年的事件分别开始于俯冲海山和俯冲脊附近，可能与下行板块地形控制的流体运动有关。我们发现，地震的时空同步与慢滑事件，其空间变化的能量率对应于应力的不均匀性浅板边界。未来对浅层地震的真实的实时监测将有助于我们理解由于浅板块边界的慢地震而引起的应力状态的变化。
Shallow slow earthquakes in subduction zones are related to spatiotemporal variations of stress on the plate boundary adjacent to a megathrust earthquake. A dense network (DONET) of cabled ocean‐bottom seismometers (OBSs) deployed in the Nankai Trough seismogenic zone, southwest Japan, has enabled real‐time monitoring of tremors. Because the amplitudes of tremor signals are very low, even when recorded by OBSs, we developed a hybrid method that simultaneously uses traveltimes based on cross‐correlations and amplitudes of waveforms to determine tremor hypocenters. We applied our method to waveforms observed during five years of continuous DONET recording from April 2016 to September 2021 to detect more than 6,500 tremors, including three major episodes in 2016, 2018, and 2020–2021. The tremors of each episode were distributed over distances of >100 km along the trench axis in two regions, southeast of the Kii Peninsula and off Cape Muroto. We also estimated seismic energy rates and found that for the three major tremor episodes, energy rates increased gradually with time. The 2018 and 2020–2021 episodes began near a subducted seamount and a subducted ridge, respectively, and were likely related to fluid movements controlled by the topography of the downgoing plate. We showed that the tremors were spatiotemporally synchronized with slow slip events, and their spatial variations of energy rate corresponded to stress heterogeneity on the shallow plate boundary. Future real‐time monitoring of shallow tremors will contribute to our understanding of changes of stress state due to slow earthquakes at the shallow plate boundary.
影响因子：
3.5
作者：
Wessel, P.;Luis, J. F.;Tian, D.
通讯作者：
Tian, D.