Preliminary magnetotelluric studies along the Hellenic Volcanic Arc: implications for the collision between the African plate and the ‘Aegea’ microplate

Abstract

From Middle-Upper Miocene time to the present the African plate has subducted under the so-called ‘Aegea’ microplate. A prominent feature of this continental collision is the past and present volcanic activity along the Hellenic Volcanic Arc (HVA), which is sited 200 km behind the frontal compressional region. Since 1986, several magnetotelluric (MT) surveys have been undertaken along the HVA, and particularly on the islands of Milos, Kos and Nisyros to determine their subsurface electrical structure. The derived electrical models have indicated very low resistivities (less than 30 Ω m) for the uppermost 10 km, which have been related to known (i.e. Milos and Nisyros) or potential (i.e. Kos) geothermal anomalies. Evaluation of the existing electrical models and subsequent 1D modelling of the broadband MT data has revealed some deeper (greater than 10 km depth) electrical features of the lithosphere below the HVA. Study of the azimuths of the major axes of the rotated impedance ellipses and the Parkinson induction arrows in the period range 10 +2–10 +4 s has led to their association with the subduction and extensional processes taking place in the Aegean. The MT results are in agreement with the observed gravity values, magnetic anomalies and the results from geotectonic, deep seismic refraction and seismological studies. Finally, proposal for the future study of the deep electrical structure of the Aegean is presented.