Spatiotemporal variations of shallow very low frequency earthquake activity southeast off the Kii Peninsula, along the Nankai Trough, Japan
Spatiotemporal variations of shallow very low frequency earthquake activity southeast off the Kii Peninsula, along the Nankai Trough, Japan
复制标题
日本纪伊半岛东南部南海海槽浅层甚低频地震活动的时空变化
DOI：
10.1029/2021jb023073
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
S.
中科院分区：
文献类型：
--
作者：
Takemura;S.;Obara;K.;Shiomi;K.;& Baba;S.
交叉相关分析应用于2004年4月至2021年3月的长期陆上宽带记录，以探测和重新定位日本Kii半岛东南部沿南开海槽的浅层极低频地震（VLFEs）。然后，我们使用基于蒙特卡罗的模拟退火方法确定了检测到的浅层vlfe的矩率函数。根据这个新的综合目录，浅层vlfe广泛分布在增生三棱镜趾下方，但具有大累积矩的浅层vlfe分布在古泽尼苏脊的西部边缘，该脊在Kii半岛东南方向俯冲。我们从长期浅层VLFE目录中得到的结果与前人在该地区的研究结果一致，表明古泽尼苏脊俯冲引起的非均质构造和应力条件促进了浅层慢震的发生。重新定位的浅层VLFE震中显示了具有相似活动区域特征的3个大震段和具有不同活动区域特征的5个小震段。三个主要时期均表现出不同起始位置、方向和速度的缓慢锋面迁移，以及几次快速的反向迁移。次要活动的发作分布在主要活动区域的一部分内的不同地点。浅层VLFE运移的不同模式可以反映出孔隙流体分布或板块边界应力条件的时间变化。
Cross‐correlation analysis was applied to long‐term onshore broadband records from April 2004 to March 2021 to detect and relocate shallow very low frequency earthquakes (VLFEs) southeast off the Kii Peninsula, along the Nankai Trough, Japan. We then determined the moment rate functions of detected shallow VLFEs using the Monte Carlo‐based simulated annealing method. According to this new comprehensive catalog, shallow VLFEs are widespread beneath the accretionary prism toe, but shallow VLFEs with large cumulative moments are localized around the western edge of the paleo‐Zenisu Ridge, which is subducted beneath southeast off the Kii Peninsula. Our results from the long‐term shallow VLFE catalog are well consistent with previous studies in this region, suggesting that heterogeneous structures and stress conditions due to the subducted paleo‐Zenisu Ridge promote the occurrence of shallow slow earthquakes. The relocated shallow VLFE epicenters illustrated three major episodes characterized by a similar activity area and five minor episodes characterized by different areas. The three major episodes exhibited slow frontal migration with different initiation locations, directions, and speeds, as well as several rapid reverse migrations. Episodes of minor activity were distributed in different locations within part of the area of major activity. Different patterns of shallow VLFE migration could reflect temporal changes in the pore‐fluid distribution or stress conditions of the plate boundary.