Department of Earth Sciences

Bobak Karimi, Nadine McQuarrie, Jeen-Shang Lin, William Harbert

The 1200 km long North Anatolian Fault (NAF) is part of an east–west trending dextral shear zone (NAF system), along the boundary between the Anatolian and Eurasian plates, that widens to the west. This widening zone of deformation complicates potential earthquake rupture paths and highlights the importance of understanding the geometry of active fault systems. In the central portion of the NAF system – just west of the town of Bolu – the NAF splits into two major faults: the northern and southern strands. These two faults diverge, almost converge, and then diverge again to border the Marmara Sea. Earthquake data from the region where the two faults converge indicate that they may be linked by an active fault. We model the active fault geometries with and without the linking fault to explore its impact on the output regional stress field (from a finite element model). These results are compared to focal mechanism records and lineament analyses to determine which geometry best simulate the stress field in a regional model. Our results show that a linking fault between the northern and southern strands of the NAF system is necessary to best match the primary stress orientations of the model with the maximum paleostress orientations inferred from deformation patterns, and observed in earthquake focal mechanisms. Furthermore, the linking fault should be a significant component in future models of the NAF system within the region.

Tectonophysics, 2014, 623, pp 14-22

DOI: 10.1016/j.tecto.2014.03.015