Fault zone conductors in Northwest Turkey inferred from audio frequency magnetotellurics

Abstract

A comparison of the electrical properties of the two main branches of the North Anatolian Fault is made based on audio-frequency magnetotelluric (AMT) surveys carried out along three typical profiles across the North Anatolian Fault Zone (NAFZ). These two branches are (i) the active northern branch (Izmit-Adapazari Fault (IAF)) where the 17 August, 1999, Izmit earthquake took place, and (ii) the less active southern branch (Iznik-Mekece Fault (IMF)). In this paper, we focus on the shallow depths (surface–1.5 km) in search for conductors near the fault zone for the purpose of comparing these two branches with each other, as well as other strike-slip faults. Phase tensor analyses and Groom-Bailey decompositions were applied to check the dimensionality of the AMT data. Following the tensor analyses and decompositions, two-dimensional inversions were carried out to yield models based on the transverse electric (TE), and transverse magnetic (TM), modes. These models suggest that the North Anatolian Fault exhibits signs of fault zone conductors (FZC) regardless of being active or less active.