Figure 1
Seismotectonic and hydrochemistry maps of Aso caldera watershed. Spatial distribution of (a) sampling stations and dominant extensional fissures (black dots with arrows), and associated horizontal land sliding (black dotted line area) observed after the 2016 Kumamoto earthquake27,28,29, (b) earthquake epicenters before (1923~: black circle) and after the 2016 main shock (red circle), and water hydrochemistry for (c) spring water and groundwater and (d) rivers based on data from 1968–1995 (Supplementary Table 1). Samples for volcano-hydrothermal fluids (labeled a–e in yellow circles of Fig. 1a; see Table 1 for details) and river waters (diamond, N1 to N5, S1 to S4 and M) in Fig. 1a correspond to the samples in Table 1 and Fig. 4, respectively. Locations of reported low resistivity zone31 for hypothesized melt finger in the deep crust (9.0–10.0 km in depth) and magma chambers beneath central volcanoes (2.0–2.5 km in depth) are shown as yellow dotted line and red dotted line, respectively. Schematic cross section A-A’ is shown in Fig. 3. Major active faults of Futagawa-Hinagu fault systems are shown as red lines. The map was illustrated by using ArcGIS Desktop (Esri).
