Fig. 1

Distribution of tectonic plates and topography of the study area. Open squares indicate the NIED F-net stations used in the present study. Red triangles denote active volcanoes. Thin black lines and the broken line denote active faults and the Median Tectonic Line (MTL), respectively. AMR, NAM, PAC, and PHS in the left figure indicate the Amur, North America, Pacific, and Philippine Sea plates, respectively. BP and IP in the right figure indicate the Boso and Izu Peninsulas