Source image of low-frequency events in Nankai trough

利用陆地地震台网在南开海槽海槽轴附近观测到了异常的甚低频地震。甚低频地震的特征是主频约为10 S，高频能量不足。这项研究表明，根据部署在震源区的海底地震仪的近距离观测，在吸积棱柱的脚趾附近发生了甚低频地震和低频地震。VLF地震具有低角度逆断层的震源机制。低频事件可能与浅吸积棱柱中的逆断层活动有关。

Anomalous very-low-frequency (VLF) earthquakes have been observed near the trough axis along the Nankai trough by land seismic networks. The VLF earthquakes were characterized by a dominant frequency of about 10 s and a lack of energy at higher frequencies. This study shows that VLF earthquakes and low frequency tremors occurred near the toe of the accretionary prism based on close range observations using ocean bottom seismographs deployed in the source area. The VLF earthquakes have a focal mechanism of a low-angle reverse fault. The low-frequency events likely relate to an activity of reverse fault in a shallow accretionary prism.