Fig. 1

Location maps of Mount Ontake volcano. a Location map of Mount Ontake volcano showing the Yashikino leveling route (black line) and the Kiso-Onsen leveling route (gray line). The triangle and squares denote the locations of the Kengamine peak of Mount Ontake volcano and the main benchmarks, respectively. The rectangles (a and b) denote the research area used to investigate seismic activity (Fig. 10). b Location map showing the GEONET stations (open squares) around Mount Ontake volcano. The rectangle and black line show the area of the location map (a) and the leveling route, respectively. c The map shows the location of active volcanoes (black triangles) in the Japanese islands, with the large triangle denoting Mount Ontake volcano