Spatial variations of stress and strain in the Zagros region, southwestern Iran

Knowing about stress variations in the Zagros region, southwest Iran is necessary to study the oblique collision between Eurasian and Arabian plates and to gain insight into the complicated tectonics of the region. In this study, earthquake focal mechanism data are used to obtain information on the state of stress in the Zagros region. We performed stress tensor inversion for different subdivisions of our dataset in the Zagros including teleseismic data, mostly from NEIC and CMT catalogs and the focal mechanisms obtained from seismic data recorded by local temporary seismic networks in the western, central and eastern Zagros, determined using the polarity method. The results show a compression in NE-SW direction, generally, but significant variations in the direction of maximum horizontal stress orientation have been observed around the Oman Line. This is in agreement with the recent studies confirming the change in crustal properties in the area. The strain rate axes estimated from published GPS velocities also has been investigated in this study. The strain rate directions show a rotation near the Hormuz area on different sides of the Oman Line similar to the stress orientations. The angular difference between the stress and the strain rate axes increases from east to west in the Zagros. The deformation partitioning due to introducing of a weak zone in Main Recent Fault on the left side of the Kazerun Fault system may explain the increase in this angular difference.