Seismic energy radiation and along-strike heterogeneities of shallow tectonic tremors at the Nankai Trough and Japan Trench
Seismic energy radiation and along-strike heterogeneities of shallow tectonic tremors at the Nankai Trough and Japan Trench
复制标题
南海海槽和日本海沟浅部构造震动的地震能量辐射和沿走向非均质性
DOI：
10.1016/j.tecto.2020.228714
复制
发表时间：
2021
期刊：
影响因子：
2.9
通讯作者：
Takemura Shunsuke
中科院分区：
文献类型：
--
作者：
Yabe Suguru;Baba Satoru;Tonegawa Takashi;Nakano Masaru;Takemura Shunsuke
浅慢地震已经被记录在靠近海沟的沿着浅板块界面上。日本近海最近的地球物理观测网络使我们能够分析南海海槽和日本海沟的浅层地震。陆上地震台站对于探测浅层甚低频地震和在部署海上观测网络之前评估其地震活动性也很重要。本研究分析了海底地震仪的数据，以估计这种地震的地震能量辐射，从中我们观察到沿走向的不均匀性。具有较高地震能量率的震颤往往具有较长的复发间隔，这也被观察到用于深震动。本研究还估计地震矩释放的浅层VLFE在日本海沟观测陆上地震台站使用绿色的功能，在当地的三维地震速度模型。比例能量是地震能量（速率）与地震矩（速率）的比值，约为10−9。位于南海海槽纪伊半岛和室户角的浅慢地震具有较高的数值（10−9-10−8），而位于南海海槽纪伊海峡和日本海沟的浅慢地震具有较低的数值（10−10-10−9），这与估计的深慢地震的数值相似。通过比较浅层地震的累积地震能量与浅层VLFE的累积地震矩，我们评估了日本海沟浅层地震和浅层VLFE的监测，这表明基于陆上地震台站数据的监测浅层VLFE可能会错过许多（最多90%）震级较小但频繁的地震矩释放。
Shallow slow earthquakes have been documented along shallow plate interfaces near trenches. Recent geophysical observation networks located offshore of Japan enable us to analyze shallow tremors in the Nankai Trough and the Japan Trench. Onshore seismic stations are also important for detecting shallow very low frequency earthquakes (VLFEs) and for evaluating their seismicity prior to the deployment of offshore observation networks. This study analyzes data from ocean bottom seismometers to estimate the seismic energy radiation of such tremors, from which we observe along-strike heterogeneity. Tremors with higher seismic energy rates tend to have longer recurrence intervals, which has also been observed for deep tremors. This study also estimates seismic moment releases of shallow VLFEs at the Japan Trench observed by onshore seismic stations using Green's function in a local three-dimensional seismic velocity model. The scaled energy, which is the ratio of the seismic energy (rate) to the seismic moment (rate), is ~10−9. Shallow slow earthquakes located off the Kii Peninsula and Cape Muroto in the Nankai Trough have higher values (10−9–10−8), while shallow slow earthquakes located off the Kii channel in the Nankai Trough and in the Japan Trench have lower values (10−10–10−9), which are similar to the values estimated for deep slow earthquakes. By comparing the cumulative seismic energy of the shallow tremors with the cumulative seismic moment of shallow VLFEs, we evaluate the monitoring of shallow tremors and shallow VLFEs in the Japan Trench, suggesting that monitoring shallow VLFEs based on data from onshore seismic stations could miss many (~90% at most) of the seismic moment releases by small magnitude but frequent events.