2D inversion of magnetotelluric data (Markazi)

Investigation of the electrical resistivity and geological structures on the hot springs in Markazi province of Iran using magnetotelluric method

(Derived from my Thesis)

M. Darijani¹,B. Oskooi¹, M. Mirzaei²

¹Institute of Geophysics, University of Tehran

²Department of Physics, Faculty of Sciences, Arak University

Submitted to Bollettino di Geofisica Teorica e Applicata (ISI). Oct. 2012.

Abstract

Markazi geothermal field is a potential geothermal system in Iran. In this paper the 12 MT stations of 2011 MT data set with elevation from 1657 to 1891 m were used along one profile. This paper detects the main features of the conductivity structures of this area. For subsurface mapping purpose, the long period natural-field MT method proved very useful. 2D inversions are conducted to resolve the conductive structures. We performed a code from Pedersen (2004) for the 1D inversion and a code from Siripunvaraporn and Egbert (2000) for the 2D inversion of DET-mode data. The MT survey has improved our understanding of the geological structure around the hot springs. The conductive layer at the surface can clearly be interpreted as the flow of the fluids in the fractures of the rocks and the top soil which saturated with penetrated water. The 2D model significantly illustrates the geothermal structures including cap rock (from 100 to 600m), reservoir (from 500 to 2000 m) and source (from 1000 m to depth). This study demonstrates how MT data can provide information about deep structure which cannot always be achieved using other geophysics techniques. MT surveys are potentially a tool for mapping geological structure beneath travertine cover around the hot springs. The faults that most likely represent active hydrothermal zones enhance the probability of conditions favorable for Enhanced Geothermal Systems. The results of our study indicate that an alteration zone is present beneath the surface; this suggests that a hydrothermal fluid circulation exists at depth.