July-December 2022 earthquake sequence in the southeastern Fars arc of Zagros mountains, Iran

Abstract

Within two hours on 01 July 2023, three earthquakes of Mw 5.8-6.0 hit the SE Fars arc, Iran. In the following months, the region characterized by the collision of the Iranian and the Arabian plate, thrust faulting, and salt diapirism was stroke by more than 120 aftershocks of mL 3.1-5.2, of which two of the largest events occurred within one minute on 23 July 2023 in spatial vicinity to each other. We analyzed both the large mainshocks and aftershocks using different techniques, such as the inversion of seismic and satellite deformation data in a joint process and aftershock relocation. Our results indicate the activation of thrust faults within the lower sedimentary cover of the region along with high aftershock activity in significantly larger depth, supporting the controversial model of a crustal strain decoupling during the collision in the Fars Arc. We resolved a magnitude difference of >0.2 magnitude units between seismic and joint seismic and satellite deformation inversions probably caused by afterslip, thereby allowing to bridge between results from international agencies and earlier studies. We also find evidence for an event doublet and triplet activating the same or adjacent faults within the sedimentary cover and the basement