SEISMOTECTONICS IMPLICATIONS OF THRUST FAULTING AND RELATED SYSTEMATIC JOINT SYSTEMS IN THE GORGAN ARDA, NE IRAN

Fault-plane solutions of recent earthquakes of Gorgan area, NE Iran, show that the most of these events have occurred by activity of thrust faulting with Strike-slip component and/or left-lateral strike-slip faulting. Obtained from the focal-mechanism of the earthquakes, calculated directions of stress axes coincide with the structural characteristics of drag folds, thrusts, and related joint system. Therefore, the seismic activities of this region have induced by the reactivation of thrust faults and related front-parallel joints, which are parallel to the NE-SW trend of thrust faults. On the whole, where there is not any geological evidence of surface faulting/rupturing due to thick layers of soil or the presence of a dense bush, we can interpret the possible spatial distributions of future earthquakes of eastern Alborz Mountains by detailed mapping of joint systems.