Fig. 3

Relocated seismicity in the Futagawa and Hinagu fault systems and around Mt. Aso. a Map view. Color image indicates the fault slip distribution of the event γ (M _w 7.0). Circles denote event locations, colored by event depth. The inset shows the fault slip model with its epicenter, indicated by the star. The blue line indicates the rim of the caldera of Mt. Aso based on the peak of the topography. b Cross sections of the relocated earthquakes at locations (A–A′ to I–I′) indicated in (a). Blue and red circles are for earthquakes before and after, respectively, the event γ at 1:25 on April 16, 2016 (local time). Gray lines indicate the fault model for the slip inversion analysis. The brown line on the top of each panel corresponds to the surface trace of active faults (Nakata and Imaizumi 2002). c Cross section of earthquakes from June 2002 to March 2016 along the X–X′ line with a width indicated by an arrow in (a) (data from the JMA earthquake catalog). Black lines are 5th and 95th percentiles of event depths, calculated every 1 km of horizontal distance for events in a 2-km wide area. Color indicates event depth