Resistivity depth sections for different depths. (a) 1 km, (b) 3 km, (c) 5 km, (d) 10 km, (e) 15 km, (f) 20 km, (g) 25 km, and (h) 30 km. The color denotes log10 (resistivity). The red triangles labeled N and M denote Naruko volcano and Mukaimachi caldera, respectively. The dotted line shows the outlines of the calderas as shown in Figure 1. The black and white dots represent hypocenters of normal earthquakes and long-period volcanic earthquakes at respective depths from the 1997 to 2011 JMA catalogue, respectively. The hypocenters were plotted with 2-km depth ranges for respective depths. Four east-west lines (L1 to L4) are profiles for the sections in Figure 5.