Delineation of shallow volcanic structures from audio-frequency magnetotelluric data beneath Ulleung Island, East Sea (Sea of Japan)

Abstract As volcanoes are closely related to the living environment of humans, in particular via natural hazards and geothermal energy, scientific studies on volcanic edifice structures required. Ulleung Island is a Quaternary island located mid-western East Sea (Sea Japan). In this study, we conducted an audio-frequency magnetotelluric (AMT) survey image substructure edifice. addition, electrical structure was interpreted from system perspective, geochemical compositions rocks, possibility presence magma reservoir. AMT data were obtained 25 stations processed using remote reference technique. Then, three-dimensional (3-D) approach reasonably adopted according dimensionality analysis. Before conducting 3-D inversion, effects topography ocean analyzed simplified synthetic model, because surrounded by sea undulating. Most distorted topographical oceanic effects; particular, significant at frequencies lower than 10 Hz. The inversion with full impedance components vertical magnetic transfer functions frequency range 10,000–1 results show that characterized two layers as follows: near-surface resistive anomalies underlying conductive layer. Considering high gradient Island, suggest layer due hydrothermal alteration basaltic potential heat source underneath. Based characteristics trachytic reservoir within shallow crustal suggested. summary, study presents geological interpretation beneath active for Graphical