Magma reservoir beneath Azumayama Volcano, NE Japan, as inferred from a three-dimensional electrical resistivity model explored by means of magnetotelluric method

Abstract An electrical resistivity model beneath Azumayama Volcano, NE Japan, is explored using magnetotelluric method to probe the magma/hydrothermal fluid distribution. one of most concerning active volcanoes capable producing a potential eruption triggered by 2011 Tohoku-Oki Earthquake. The three-dimensional reveals conductive magma reservoir (< 3 ?m) at depths 3–15 km below sea level (bsl). 67% and 90% confidence intervals are 0.2–5 ?m 0.02–70 ?m, respectively, for reservoir. We assumed dacitic melt + rock shallow depth 4 bsl andesitic greater 9 bsl. interval cannot be explained condition This suggests that very hydrothermal fluids coexist with in part For bsl, interpreted as water-saturated (8.0 weight %) melt–mafic complex volume fractions than %, while shear wave velocity requires and/or fraction 6–7 % depth. Considering hydrous phase likewise required explain wide range resistivity. Mogi inflation source determined from geodetic data lies on resistive side near top boundary 2.7 or 3.7 Assuming region above upper bound composed rock, 5 which percolation threshold porosity an effusive eruption. indicates characterizes region.