The kinematics of the Dasht-e Bayaz earthquake fault during Pliocene-Quaternary: Implications for the tectonics of eastern Central Iran

Abstract

The Arabia-Eurasia convergence is accommodated across the Iranian plateau and surrounding mountain ranges. Strike-slip faults play significant roles in the current deformation of the Iranian plateau and were responsible for several moderate to large earthquakes, especially in east of Iran. The sinistral Dasht-e Bayaz fault shows conspicuous seismic and geological activities, while the role of the fault in the accommodation of active convergence is still debated. This paper focuses on the Pliocene-Quaternary to present-day states of stress in the region affected by the Dasht-e Bayaz fault. We applied the fault-slip inversion technique to both kinds of seismologic and geological fault slip data. The inversion results indicate a mean N045±5°E trending σ1 in the modern stress field, which agrees with the present-day tectonic regime (regional N050±05°E trending σ1) deduced from the inversion of earthquake focal mechanism data. The paleostress state is characterized by a N135±15°E trending regional mean σ1, with a transpressional stress regime; E-W faults of the region such as the Dasht-e Bayaz fault were reverse dextral in this paleostress field. We show that the shift in fault kinematics during the Pliocene-Quaternary times has not been restricted to northeastern parts of the Iranian plateau. The cross-cutting relationship between active N-S dextral and E-W sinistral faults indicates a crosswise to conjugate fault arrangement in the middle and the eastern end of the Dasht-e Bayaz fault. Integrating our results at a larger regional scale, we present a kinematic model in which the region between Lut and Kopeh Dagh is divided by the Doruneh fault into two tectonic domains. In the northern domain, active convergence is taken up by the extrusion of fault-bounded crustal blocks while, in the southern domain the convergence is accommodated through crosswise strike-slip faulting accompanied by reverse/thrust faulting in confining wedges.

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