Probing the relationship between electrical conductivity and creep through upper crustal fluids along the western part of the North Anatolian Fault with three-dimensional magnetotellurics

Abstract Seismic characteristics of any fault system are affected by the relationship between the relevant stress regime and the fluid content of a region. Under persistent stress accumulation, fluids can facilitate earthquake generation due to their effect on frictional forces. In this study, Armutlu Peninsula serves as a suitable example to investigate the role of fluid-rich environments in seismicity distribution. In the context of electrical resistivity characteristics provided by a fluid-sensitive geophysical method, namely magnetotellurics, seismogenic properties of the western part of the North Anatolian Fault are examined from its mechanical attributes to fault – fluid relationship. Near the epicenter of the catastrophic 1999 Izmit Earthquake, Hersek region appears as a fluid-rich environment between shallow creeping and aseismic strain releasing portions that bound highly resistive Armutlu Peninsula. Conductor related to fluid-rich environment extends until depth of approx. 10 km and precludes earthquake activity along the fault zone. High amount of fluids concentrated on particular conductive regions, may restrain earthquake distribution with the absence of mechanically strong structures around the fault zone. As a potential asymmetric damage zone appears around the NAF, both aftershock distributions of the 1999 Izmit Earthquake in the following three months and long-term earthquake data show a clear tendency for concentration on resistive parts of the study area. Fluid-rich regions possibly indicate the endpoints of the segments in the NAF. The final electrical resistivity model produced in this study reveals that interpreting tectonic, seismic or geological aspects of any fault system can plausibly be dependent on counting spatial extensions of fluid-rich environments. In order to correctly assemble interdisciplinary findings, it may be essential to consider more features than vertical extensions of conductive zones which, mostly indicate fluid-bearing regions.