Deep Conductivity Structure of the North Anatolian Fault Zone and the Istanbul and Sakarya Zones Along the Gölpazari-Akcaova Profile, Northwest Anatolia

Abstract

Magnetotelluric (MT) measurements at six locations along a 90-km profile across the area between Gölpazari and Akcaova have been modeled in two dimensions to increase understanding of the deep conductivity structure of the western part of the North Anatolian fault zone (NAFZ) and the Istanbul and Sakarya zones. It is well known from surface geology that the branch of the NAFZ that passes through the Pamukova Valley with an E-W strike separates the region into two sub-areas, containing contrasting sets of geological features. These two areas also exhibit significant differences in terms of their deep conductivity structure. Electrical resistivity is quite low (10 ohmm) south of the fault at an approximate depth of 26 km, compared to the area north of the fault zone. This low-resistivity zone may provide an indication of partial melting at this depth. In the northern part of the profile beneath Ücgaziler (DUC) and Akcaova (DAK), a five-layered conductivity sequence obtained by magnetotelluric modeling and the magnetotelluric model has been examined in light of the surface geology. It is concluded that layers in the conductivity model may correspond to fragments of the Istanbul zone and the Sakarya continent, as well as the ophiolitic slab in between.