Fig. 1

Epicenters and focal mechanisms of the mainshock and foreshock of 2016 Kumamoto, Japan, earthquake sequence. Red and black beach balls represent the focal mechanisms of the mainshock and foreshock, respectively. Open triangles represent KiK-net stations; the black and red ones are located in the volcanic and non-volcanic areas, respectively. Black solid circles represent Kumamoto Castle and Minami Aso village. The inset shows the tectonic setting of the Kyushu region. The subduction direction of the Philippine Sea Plate into the Eurasian Plate is shown in red triangular fronts; the study area, Kyushu region, is indicated by a red rectangle; boundaries of tectonic plates are shown in black and red solid lines