Magnetotelluric measurements on the Methana Peninsula (Greece): modelling and interpretation

As a first deep geophysical survey, thirteen magnetotelluric and magnetovariation soundings in the period range of 0.0085-6000 s have been carried out in the Methana Peninsula and Trizina area (Greece), which form the western part of the active Hellenic Volcanic Are. Data have been processed using robust techniques and further analysed using decomposition methods in order to find the regional azimuth. By using the smooth inverse of Smith and Booker (J. Geophys. Res. 96, 3905-3922, 1991), the 2-D modelling has resolved a low-resistivity area ((30 Omega m) at depths of 2-3 km beneath the volcanics, whereas elsewhere the resistivity is much higher (>100 Omega m). Parkinson induction arrows also at the range 0.01-0.1 s point towards the centre of the peninsula. The conductivity anomaly is interpreted as being connected with the volcanic history of Methana, as a cooler remnant of former magmatic activity. The contrast with the much higher resistivities suggested at depths >5 km, is discussed in terms of fluid mobility, limitation of the MT method and extensional processes in the southern Aegean. (C) 1999 Elsevier Science B.V. All rights reserved.