The NW–SE trending Zagros orogenic belt was initiated during the convergence of the Afro–Arabian continent and the Iranian microcontinent in the Late Cretaceous. Ongoing convergence is confrmed by intense seismicity related to compressional stresses collision-related in the Zagros orogenic belt by reactivation of an early extensional faulting to latter compressional segmented strike–slip and dip–slip faulting. These activities are strongly related either to the deep-seated basement fault activities (deep-seated earthquakes) underlies the sedimentary cover or gently dipping shallow-seated décollement horizon of the rheological weak rocks of the infra-Cambrian Hormuz salt. The compressional stress regimes in the diferent units play an important role in controlling the stress conditions between the diferent units within the sedimentary cover and basement. A signifcant set of nearly N–S trending right-lateral strike–slip faults exists throughout the study area in the Fars area in the Zagros Foreland Folded Belt. Fault–slip and focal mechanism data were analyzed using the stress inversion method to reconstruct the paleo and recent stress conditions. The results suggest that the current direction of maximum principal stress averages N19°E, with N38°E that for the past from Cretaceous to Tertiary (although a few sites on the Kar-e-Bass fault yield a diferent direction). The results are consistent with the collision of the Afro–Arabian continent and the Iranian microcontinent. The diference between the current and paleo-stress directions indicates an anticlockwise rotation in the maximum principle stress direction over time. This diference resulted from changes in the continental convergence path, but was also infuenced by the local structural evolution, including the lateral propagation of folds and the presence of several local décollement horizons that facilitated decoupling of the deformation between the basement and the sedimentary cover. The obliquity of the maximum compressional stress into the fault trends reveals a typical stress partitioning of thrust and strike– slip motion in the Kazerun, Kar-e-Bass, Sabz-Pushan, and Sarvestan fault zones that caused these fault zones behave as segmented strike–slip and dip–slip faults.
کلید واژگان :Fault–slip data · Earthquake focal mechanism · Paleo-stress · Recent tectonic stress · Zagros · Iran
ارزش ریالی : 600000 ریال
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