Geophysical investigations of the Seferihisar geothermal area, Western Anatolia, Turkey

Self-potential (SP), magnetic and very low frequency electromagnetic (EM-VLF) surveys were carried out in the Seferihisar geothermal area to identify major and minor fault zones and characterize the geothermal system. The SP study provided useful information on the local faults and subsurface fluid flow. The main SP anomalies appear mostly along and near active fault zones in the area of the Cumalı, Tuzla and Doğanbey hot springs. Two of these anomalies near the Tuzla hot springs were further evaluated by SP modelling. Total magnetic field values increase from the Doğanbey to the Cumalı hot springs. Modelling performed on the magnetic data indicates that between these two spring areas are four different regions or units that can be distinguished on the basis of their magnetic susceptibility values. Fraser filtering of EM-VLF data also indicates that there are three significant conductive zones in the regions around the Cumalı, Tuzla and Doğanbey hot springs, and that they lie between important fault systems. The EM-VLF and total (stacked) SP data show that the conductive tilt anomalies obtained by Fraser filtering generally coincide with negative SP areas.According to our geophysical investigations, new exploratory wells should be drilled into the conductive zones located between the Cumalı and Tuzla hot springs. We further recommend that resistivity and magnetotelluric methods be carried out in the area to obtain additional information on the Seferihisar geothermal system.