Open Access

Geoelectric structure in the Andaman Islands using magnetotelluric studies

Earth, Planets and Space200658:BF03353386

https://doi.org/10.1186/BF03353386

Received: 29 June 2005

Accepted: 30 December 2005

Published: 17 February 2006

Abstract

Magnetotelluric studies over the Middle Andaman islands have delineated a NNE-SSW trending suture, along which the Andaman flysch and the underlying Igneous crust subduct eastwards along a high angle thrust with a dip angle of about 60°. The Andaman flysch, which have thickness varying between 4 and 10 km are delineated up to depth of about 17 km along the observed thrust. The crust to the west of the suture has a high resistivity of more than 10000 Ω-m, as against a moderate resistivity of about 1000 Ω-m observed in the eastern part. The complex variations in its thickness and resistivity are indicative of the intense tectonic activity that this juvenile crust has experienced since the Cretaceous. The crust is underlain by a low resistivity, which could be due to the presence of fluids generated by the metamorphosis of the subducting crust and also expelled from the rocks at deeper levels. However the earthquake focal depths, extending up to about 150 km suggest that the lithosphere may be sufficiently solidified to permit strain accumulation at this depth. Thus the extent of the partial melt may be limited to about 1%.

Key words

Magnetotelluric electrical resistivity Andaman-Nicobar islands