A new magnetotelluric (MT) survey, along with new topographic parametric sonar (TOPAS) profiles and geological field observations, were carried out on the Deception Island active volcano. 3-D resistivity models reveal an ENE–WSW elongated conductor located at a depth between two and ten kilometres beneath the south-eastern part of the island, which we interpret as a combination of partial melt and hot fluids. The emplacement of the melt in the upper crust occurs along the ENE–WSW oriented, SSE dipping regional normal fault zone, which facilitates melt intrusion at shallower levels with volcanic eruptions and associated seismicity. Most of the onshore and offshore volcanic rocks are deformed by high-angle normal and sub-vertical faults with dominant dip-slip kinematics, distributed in sets roughly parallel and orthogonal to the major ENE–WSW regional tectonic trends. Faults development is related to perturbations of the regional stress field associated with magma chamber overpressure and deflation in a regional setting dominated by NW–SE to NNW–SSE extension.
