Fig. 5From: Anatomy of active volcanic edifice at the Kusatsu–Shirane volcano, Japan, by magnetotellurics: hydrothermal implications for volcanic unrestsa Simplified W–E resistivity section in Fig. 4b. The rectangles on the terrain denote the observation sites. The white and black stars and the green “X” symbols are the same as in Fig. 4. The swarm dots with bigger and with smaller circles denote the hypocenters of microseismic events during 2014 unrest, and out of this active period, respectively. b Pressure–temperature projection of hydrothermal fluid phase diagram for H2O and CO2 (after Hutnak et al. 2009). Two curves which end with solid circles denote the liquid–vapor coexistence curves of pure CO2 and pure H2O with their critical points (CP). C2 may be an established fluid path from the supercritical fluid. In contrast, if episodic large gas flux breaks the silica cap, breakage of the silica cap may flush the fluid upward in the hydrostatic domainBack to article page