Seismology of the 2017 Hojedk earthquakes (MN 6.0–6.1), Kerman province, SE Iran

Abstract

Three moderate earthquakes on 1 and 12 December 2017 with MN magnitudes of 6.0–6.1 (MS1, MS2 and MS3) occurred in the SE Iran. They happened in the area between Nayband and Kuh Banan fault systems, NE of the Kerman metropolice. We combined satellite imagery, seismicity, focal mechanism solutions, strong motions, and Coulomb stress to investigate the earthquakes. These events were located near the southeastern splay of the N-S Lakar Kuh right-lateral strike-slip fault. Active tectonics of the Lakar Kuh fault as well as the earthquake deformations were confirmed by satellite imagery and field photographs, respectively. Hypocenters of the three Mw ~6.0 earthquakes and their aftershocks indicated a migration of faulting from the SE towards the NW. According to high resolution satellite imagery, the third earthquake produced ~6 km of coseismic surface rupture in the alluvial fan deposits (east of Mian Kuh) with maximum deformation in the middle part. The focal mechanisms of both the mainshocks and the strongest aftershocks (MN > 4.6) determined from P wave first motions indicated ~NW-SE fault strikes for the 3 events (dipping SW for MS3), with dominant reverse slip and minor strike-slip components. General northwestward migration of mainshocks as well as strong motions recorded at accelerometers nearby showed evidence for northwestward rupture directivity in all three earthquakes. It was in accordance with the rupture geometry, hypocenter and centroid depth of MS3. The Coulomb stress investigation also revealed that the aftershocks of the 3 events partially covered the increasing areas of Coulomb stress.