A Geothermal Exploration MT Data Set and Its 3-D Inversion Using Two Different Codes: an Example from Western Turkey

Abstract

In June 2013 a 51-station magnetotelluric (MT) survey was carried out to investigate the geothermal prospectivity of an area located in the Aegean Coastal Belt in northwestern Turkey. The metamorphic unit that is generally inferred to host the geothermal reservoir is of Paleozoic age and contains a granitic batholith which intruded the unit during volcanic activity in the Oligo-Miocene period. These metamorphic rocks are furthermore overlain by a Miocene volcanogenic unit which developed during several phases of volcanism. The youngest geological unit consists of alluvial sediments deposited during the Quaternary. Structurally, the area was formed by extensional tectonic movements associated with N-NE to S-SW oriented fault systems and normal faulting. The acquired MT time-series data are processed using industry standard processing software. After data processing, Egbert’s (2012) ModEM code and Mackie’s (2012) magnetotelluric inversion code are used for the 3-D inversion of the MT responses. The 3-D modelling results are compared and we evaluate the differences between the two 3-D resistivity models and discuss the implications any differences and similarities have for the definition of the geothermal reservoir and resource.