Document Type : Original Research Paper
Authors
1 Ph.D. Student, Department of geology, Faculty of Science, Tarbiat Modares University, Tehran, Iran
2 Associate Professor, Department of geology, Faculty of Science, Tarbiat Modares University, Tehran, Iran
Abstract
In this paper, the structural relationship between two main structural features of the Zagros suture zone, that is, the Main Zagros Reverse Fault (MZRF) and the Main Recent Fault (MRF) in Kurdistan area has been studied in more detail. This provides information as to the structural evolution and seismotectonics of the Zagros suture zone. Around latitude 36, the Sardasht segment of the MRF cut the MZRF and toward southeast part of this intersection, the MRF is the only major fault between the Zagros fold- thrust belt and the Sanandaj- Sirjan zone. Here, segments of the MZRF can be seen in the MRF zone, which represents the younger activity of the MRF. Our investigation show that there is a right- hand bending between the Piranshahr Fault in the northwest and the Marivan Fault in the southeast (between latitudes 35 ̊, 30' and 36 ̊, 30'). On the southwest and northeast edges of this releasing bend, the Sardasht and Baneh faults are located that have both strike-slip and normal components. Considering geometric and kinematic aspects of the curved segment of the MRF (Sardasht Fault), as well as the paleostress studies of this segment, it can be said that the Sardasht Fault with N30W trending fault has deviated from the main displacement vector (N60W) and hence has a normal component. Therefore, this fault accommodates dextral and transpressional movements between the Zagros fold- thrust belt and the Sanandaj-Sirjan zone and its normal movements arising from the right hand bending of the MRF. Paleostress analysis (using the Multiple Inverse Method) shows separate stress fields for different movements. Paleostress fields have a close correlation with the stress fields obtained from the focal mechanism of the earthquakes located along the Zagros suture zone. This correlation shows that the obtained stress fields are belong to younger activity. Displacement of the MZRF by the MRF caused significant heave in the MZRF and thus it does not expose at the surface between latitudes 35 ̊, 20' and 36 ̊, 00'.
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