Vol. 10, No. 2 – Summer 2008

۳D Mechanical Modeling of the GPS Velocity Field Along the Main Recent Fault and Kazerun Fault (Zagros, Iran)

H.R. Nankali, F. Sobouti, B. Voosoghi, K. Hessami, M. Talebian, A. Walpersdorf and F. Tavakoli

The NW-SE trending Zagros mountains form a linear belt more than 1500km in length, from eastern Turkey in the NW to the strait of Hormuz in the SE. They result from the continental collision between the Arabian plate and Central Iran that started during the Miocene [e.g. 40], or perhaps earlier in Cenozoic time. A threedimensional visco-elastic finite element model was developed in order to simulate long-term, displacement rate along the Main Recent Fault and Kazeun fault by adjusting the effective fault friction. In order to undertake this process, a friction range of 0.02-0.3 was used for a fault. A model was constructed using spatially varying crustal thickness, geothermal gradient, and two major faults. The mesh covers a rectangular area in the Zagros with horizontal dimensions of 1500km×۶۰۰km and a depth extent of 70km. Structural boundaries are derived from several deep seismic soundings carried out in the area. The constructed model is first used in the calculation of thermal initial condition and secondly in analyzing the deformation. The structure of the fault zones is represented by contact surface with the Coulomb friction law. One of the most striking results of our rheological test is that the faults are locked if the friction exceeds 0.2. By comparing our results with geodetic measurements [48, 51], a realistic model is defined in which the displacement rates on the MRF and Dena, Kazerun and Borazjan faults reach 3.3mmyr-1, 2.8mmyr-1, 1.9mmyr-1, 0.5mmyr-1 for a fault friction of 0.02. These results strongly suggest that MRF and Kazerun fault are weak faults like San Andreas and North Anatolian faults.

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