Fig. 6

Comparison of the observed (red arrows) and calculated (blue arrows) tilt changes. The open crack model used to calculate tilt changes is indicated by red rectangles. The blue rectangles show the open cracks determined from the tilt changes observed during the 2001 unrest (Daita et al. 2009). A nearly vertical open crack at a shallow depth that was obtained from InSAR data is indicated by small black rectangles (Doke et al. 2018). The eruption center is illustrated by a white circle. Black dots are earthquakes that occurred at 7:00 a.m.–12:00 p.m. on June 29, 2015. Blue and red circles are hot spring wells. Hot springs represented by red circles are chemically close to hydrothermal water from magma body at deeper part