Aftershocks study of the 2006 Silakhur earthquake (Zagros, Iran): seismological evidences for a pull-apart basin along the Main Recent Fault, Doroud segments

The Doroud segment of the Main Recent Fault ("MRF") is studied by installing a local seismic network of 35 short-period stations for a period of 13 weeks from 21 June 2007 to 19 September 2007 in the Silakhur region of the Zagros continental collision zone, close to the epicenter of the 31 March 2006 Silakhur earthquake (M (w) similar to aEuro parts per thousand 6.1). Our seismic network also covers the Qale-Hatam and Vanaei segments of the MRF and part of the Nahavand fault. We investigate the geometry and mechanism of the causative fault(s) of the 2006 Silakhur earthquake using aftershocks recorded by the dense local network. Most of the aftershocks in this region are located at a depth of 4-11 km, shallower depth than usual for other seismic zones in the Zagros. The distribution of the aftershocks along the course of the river indicates that older faults in the Silakhur region have been activated during the 2006 earthquake and only a few aftershocks have occurred on the Doroud fault. Tensional and compressional components in the northern part of the Doroud fault are interpreted as a pull-apart basin which has been activated by the right-lateral strike-slip movement of the Doroud fault.