Geoelectric structure of inland area of the Gökova rift, southwest Anatolia and its tectonic implications

Abstract

A geoelectrical survey using vertical electrical sounding was carried out to identify the geoelectric model of graben structure within the Gökova rift, since it can provide further useful information on the north–south extension in the western Anatolia. Over 60 Schlumberger electrical soundings were made in the inland area of the rift, using current electrode spacings up to 1500 m. The geoelectrical models are obtained from two-dimensional resistivity inversion based on observed apparent resistivities, since one-dimensional stratified earth models cause several errors due to lateral resistivity changes. The resistivity maps and the two-dimensional geoelectric models indicate that the tectonic structure is comparatively complex, and that the structural pattern is disturbed by numerous fault zones. Interpretation of geoelectrical structure suggests that the inland area of the Gökova rift has an asymmetric graben structure as observed in both the Gediz and Büyük Menderes grabens of western Anatolia. The strong lateral variations in resistivity values at the northern and southern margins of the area indicate the edges of the basin. Abrupt variations in lateral resistivity across the profiles reflect the signature of east–west-trending faults in southern and northern margins of the Gökova graben. A conducting anomaly that is well depicted in all resistivity maps and the two-dimensional geoelectric structure show that the Plio-Quaternary deposit in the eastern part of the area is thicker (up to 140–150 m) and the basement is deeper. The irregular development of sedimentaries in the basin and the short faults trending northwest–southeast identified from two-dimensional geoelectrical models, suggest the cross-cutting relationship between the Gökova and Yatağan–Muğla rifts.