Satoshi Annoura

Total energy of deep low‐frequency tremor in the Nankai subduction zone, southwest Japan

We estimated the total seismic energy of deep low-frequency tremor in the Nankai subduction zone, southwest Japan, over an 11 year period. For precise estimation, the continuous time sequence of tremor activity was carefully detected using a procedure designed to minimize false-negative detections. The estimated spatial distribution of accumulated total energy of tremor indicates high-energy area in the western Shikoku region. Tremor activity rate, defined as the yearly average of total tremor energy per unit area, was investigated in each area throughout the Nankai subduction zone. The tremor activity rate was spatially variable, being high in areas west of the Kii Channel (the channel is marked by a complex plate geometry) and low in areas east of the channel. The plate convergence rate shows the same spatial pattern as that for tremor activity. We infer that tremor activity is influenced by accumulated strain due to plate convergence.