Dynamic deformation of the accretionary prism excites very low frequency earthquakes

We have detected anomalous very‐low‐frequency earthquakes within the accretionary prism along the Nankai Trough, southwestern Japan. Centroid moment tensor inversion analysis reveals that the earthquake hypocenters are distributed at ∼10 km depth above the upper surface of the subducting Philippine Sea Plate, and within 50–70 km landward of the trough axis. The focal mechanisms indicate reverse faulting. Their hypocenters are distributed beneath a deformation zone of an accretionary prism in sea‐floor topography. These observations suggest that the occurrence of very‐low‐frequency earthquakes is related to numerous reverse fault systems within the accretionary prism, and that the earthquakes reflect the dynamics of deformation within this accretionary prism.