INVESTIGATION OF THE CONTEMPORARY STRESS STATE IN CENTRAL ZAGROS

Among the present active belt, the Zagros mountain fold and thrust belt located in SW Iran, is one of the most seismically active regions in the world. It results from the collision of the Arabian plate with continental blocks of Central Iran. The studied area extend between 50 to 54E, characterizing by N-S-trending right laterally strike slip faults such as Kazerun, Kareh-Bas, Sabzpushan and Razak-Sarvestan.The main purpose of present study is to find the state and direction of contemporary stress investigated by using inversion methodology. Furthermore specification mechanism of faults that have different direction and trend based on stress state near these faults. The present – day state of stress responsible for active faulting in central Zagros determined by inversion of focal mechanism from moderate to large (... ) earthquakes. Furthermore, in this study we determined the stress tensor for local micro earthquakes focal mechanisms that have solved by first polarity of P wave (Tatar et.al, 2003).This method for inversion proposed by Carey- Gailhardis and Mercier (1987).According to our data and deduced results, in central Zagros, the Arabia-Eurasia convergence is taking up by strike-slip faulting along NEE trending left lateral and NWW trending right lateral faults, as well as reverse to oblique-slip reverse faulting along NW trending faults. The direction of maximum shear stress(δ1 ) vary about 35°of the northwest to southeast in central Zagros and about tectonic regimes we can told that compression tectonic regimes govern to over Zagros and strike slip faults that existed in that, regionally controls this regimes.

Keywords:

Active Tectonics , Focal Mechanisms , Contemporary Stress , Stress Tensor