Seismotectonics of the Bitlis–Zagros Fold and Thrust Belt in Northern Iraq and Surrounding Regions from Moment Tensor Analysis

Abstract

Northern Iraq represents part of the convergent plate boundary between the Arabian and Eurasian plates. The collision zone between these two plates is manifested by the Bitlis–Zagros Fold and Thrust Belt. This belt is one of the most seismically active regions among the present active belts. This study intends to improve our knowledge on the seismotectonic activities in northern Iraq and the surrounding areas. To reach this goal, we used the waveform moment tensor inversion method to determine the focal depths, moment magnitudes, fault plane solutions, and directions of the principal stress axes of 25 events with magnitudes ≥3.5. The seismic data of these events were collected from 54 broadband stations which belong to the Kandilli Observatory and Earthquake Research Institute, the Incorporated Research Institutions for Seismology, the Observatories and Research Facilities for European Seismology, and the Iraqi Seismological Network. Computer Programs in Seismology, version 3.30 (Herrmann and Ammon2004), was used for analysis. The results show that the focal depth of these events ranged from 15 to 25 km in general. The fault plane solutions show that the strike-slip mechanism is the most dominant mechanism in the study area, usually with a reverse component. The stress regime shows three major directions; north–south, northeast-southwest, and east–west. These directions are comparable with the tectonic regime in the region.