2D inversion of magnetotelluric data (Mahallat)

2D inversion of the magnetotelluric data from Mahallat geothermal field in Iran using finite element approach

M.Darijani¹, B.Oskooi¹

¹Institute of Geophysics, University of Tehran, Iran.

Accepted to Arabian Journal of Geosciences [Springer] (ISI). Feb. 2013.
Accepted to Istanbul International Geophysical Conference, September 2012, Oral.

Abstract

    

A magnetotelluric (MT) survey was conducted on Mahalat geothermal field located in west central Iran. The region of Mahalat is a popular tourist spot due to the occurrence of hot water springs and one of the greatest geothermal fields in Iran. The purpose of the first MT survey in this area is to provide more information on the geoelectrical structure of this important geothermal reservoir. MT is widely utilized for surveying geothermal areas such as Mahalat. In thermal areas, the electrical resistivity is substantially different form and generally lower than in areas with colder subsurface temperature. The selected MT profiles in the region cross over the hydrothermally altered zones and different geological structures. Data were acquired along two profiles crossing the Mahalat hot springs with a total of 28 MT stations in a frequency range of 8000 Hz to 0.008 Hz. Spacing between stations was kept 500 m for a better resolution. We have used the code MT2DInvMATLAB for inversion using the method of finite elements (FEM) for forward modeling. Apparent resistivity and phase data of TE, TM and TE+TM modes along each profile were modeled. The geothermal fluid reservoir is resolved at 1000 to 3000 m depth and the geothermal resource is estimated to be located at 7000 m or deeper.