Fig. 1
a, b Show the plots of observed horizontal vector PGAs and PGVs, respectively. A star denotes epicenter of the mainshock. Triangles and dashed red line denote active volcanoes and volcanic front line, respectively. c Enlarged view of the rectangular area drawn around the epicenter in a with additional information. Numbers in parentheses denote the values of horizontal vector PGAs (cm/s2) and PGVs (cm/s), respectively, at recording stations color-coded by PGAs. The magenta circles denote aftershocks of Mj ≥ 2 for the 9 days after the mainshock. The rectangle denotes the surface projection of an approximate fault plane. d Vertical section of JIVSM (Japan integrated velocity structure model) along the profile A–A′ shown in c. A red dashed line denotes the intersection line of the inferred fault plane with the vertical section