Upper crustal electrical resistivity structures in the vicinity of the Catalca Fault, Istanbul, Turkey by magnetotelluric data

Abstract

A magnetotelluric survey was performed at the Catalca Region, west of Istanbul, Turkey with the aim of investigating geoelectrical properties of the upper crust near the Catalca Fault and its vicinity. Broadband magnetotelluric data were collected at nine sites along a single southwest-northeast profile to image the electrical resistivity structure from surface to the 5 km depth. The dimensionality of the data was examined through tensor decompositions and highly two-dimensional behavior of the data is shown. Following the tensor decompositions, two-dimensional inversions were carried out where E-polarization, B-polarization and tipper data were utilized to construct electrical resistivity models. The results of the inversions suggest: a) the Catalca Fault extends from surface to 5 km depth as a conductive zone dipping to southwest; b) the thickness of the sedimentary cover is increasing from SW to NE to 700 m with low resistivity values between 1-100 Omega m; c) the crystalline basement below the sedimentary unit is very resistive and varies between 2000-100000 Omega m; d) a SW-dipping resistivity boundary in the northeastern part of our profile may represent the West Black Sea Fault.