Influence of the Basement Strike-Slip Fault on the 2005 and 2014 Earthquakes, Qeshm Island, Iran

The Zagros belt in southern Iran is amongst the world s most seismically active mountain ranges that accommodates a significant portion of the convergence between Arabian and Eurasia Plates. Due to the larger earthquakes in Zagros, which have strike-slip focal mechanisms without any coseismic ruptures at the surface; it is important to identify the source of these earthquakes in the basement. The 2005 and 2014 earthquakes with Mw=5-6 in Qeshm Island are examples of them. The NE-trending Gachin fault zone is one of the main transverse faults that cross cut the major structures of Bandar Abbas zone and continues to the Persian Gulf; in which deformations of the fault are overprinted on the major structures. Based on the field, remote sensing and sismotectonic studies; the Gachin fault zone is the main cause of the recent deformations on the Quaternary sediments in Qeshm Island and its activities are continuing to present time; therefore, the above-mentioned earthquakes were caused by this fault. In other words, the convergence between Arabian and Eurasia Plates is in favour for the reactivation of Gachin fault zone in the basement as earthquakes.