Co-seismic slip of the 18 April 2021 Mw 5.9 Genaveh earthquake in the South Dezful Embayment of Zagros (Iran) and its aftershock sequence

Abstract

On 2021 April 18, an Mw 5.9 earthquake struck the Genaveh region in the south Dezful embayment of the Zagros, Iran. Here, we investigate the active tectonics of the region, the geometry and slip distribution of the causative fault plane, and its aftershock behavior. We applied a combination of different geodetic and seismological methods (slip distribution inversion of the mainshock using Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR), relocation, and moment tensor inversion of aftershocks and background seismicity of the region). Co-seismic InSAR modeling shows that the slip is confined to the sedimentary cover at depths of 4-7 km with a maximum slip of 1 m and highlights the influence of lithology in the rupture propagation. Moment tensors and centroid depths of aftershocks down to Mw 4 show that the distributed aftershocks sequence is dominated by reverse faulting at centroid depths of 4-10 km. The causative fault is compatible and parallel to the trend of the Gulkhari anticline and the coseismic uplift of the Genaveh earthquake implies that the growth of this particular fold is linked to the fault(s). However, still, due to the absence of surface rupture, the clear relationship between buried faulting and surface folding remains unclear.