Quaternary deformation patterns in East–Central Iran, constrained by coseismic–postseismic displacements of the 2017 Hojedk triplet earthquake in the Kerman Province

Abstract

The Central Iranian Microcontinent (CIM) in east-central Iran is located north of the active Arabia–Eurasia collision zone. Here, we report on the structure, deformation patterns, and earthquake occurrences along the dextral Lakar–Kuh and Godar fault systems in the CIM. The geometry of these fault systems marks a major restraining bend responsible for surface and rock uplift in the Plio–Pleistocene that produced the Mian Kuh mountain range. The 2017 Hojedk triplet earthquake (Mw = 5.8–6.0) occurred in the Mian Kuh Range. Sentinel–1 A Interferometer Synthetic Aperture Radar (InSAR) images (descending and ascending) were used to extract the coseismic displacements associated with the earthquake and its aftershocks. The results indicate a maximum displacement of ∼20 cm, corresponding to hanging wall uplift along the radar Line-of-Sight (LOS) direction. The Geodetic Bayesian Inversion (GBIS) of the coseismic deformation indicates that the causative faults of the Hojedk earthquakes were two reverse faults with NW–SE–strikes and SW–dips, with minor dextral slip components. Given the focal mechanism solutions and the epicenter locations of the triple earthquake sequence, we infer that these faults at the southern termination of the Lakar–Kuh Fault represent two segments (with different dip angles) of a previously unrecognized, blind reverse fault (a splay of the Godar Fault at depth). The Hojedk Earthquake and the geometry and kinematics of its causative faults highlight the strong potential of seismic hazard zones along the strike-slip fault systems in the CIM.