Fig. 13

Velocity cross sections for the 200-m cell model in the crust beneath the Aira caldera: (a) velocity distribution and (b) velocity perturbation distribution. Red contour lines in (a) indicate a velocity of 6.4 km/s; whereas the region surrounded by the white thick solid line denotes the deep low-velocity zone (LVZ). In (b), the region surrounded by the black thick solid line expresses the deep LVZ (same as that in (a)). In (a) and (b), the ellipse drawn by a broken line indicates the pressure source reported by Hickey et al. (2016). Cross and plus symbols indicate the spherical pressure sources-A and -B estimated by Hotta et al. (2016) and Iguchi et al. (2013), respectively. Volcano-tectonic (VT) (white circles) and low-frequency (LF) (yellow circles) earthquakes are also plotted. Other symbols are same as those in Fig. 6