[U-02] Remote Sensing Role in Sustainable Development

[U02-04] Fault slip distribution of the 14 November 2021 Fin doublet earthquakes, Southeast Iran, from InSAR measurements

*Jiaqing Wang^1,2, Yosuke Aoki², Yan Cui^3,2, Lang Xu^4,2, Guohong Zhang⁵, Yingfeng Zhang⁵, Guangli Su¹, Iraj Rouhi⁶ (1.First Monitoring and Application Center, China Earthquake Administration, China, 2.Earthquake Research Institute, the University of Tokyo, 3.Hohai University, China, 4.Southwest Jiaotong University, China, 5.Institute of Geology, China Earthquake Administration, China, 6.University of Tehran, Iran)

Keywords:Fin earthquake, blind thrust fault, InSAR, BOI

The ambiguity in the fault geometry of buried thrust earthquakes of moderate magnitude occurring in folded thrust zones always brings uncertainties in understanding the interplay between faulting and folding. On 14 November 2021, doublet earthquakes (M_w6.1 and M_w6.4) struck the Fin area in the southeastern Zagros Mountains, providing an opportunity to investigate the interaction between folding and faulting. We use DInSAR and BOI to obtain the coseismic surface deformation with different viewing geometries based on Sentinel-1A and ALOS2 PALSAR images, and reconstruct the 3D deformation by combining all measurements using a weighted least-squares method. We find significant lateral motion along the NNE in the uplifted region near the epicenter, which cannot be reproduced by either the slip on a single N or S dipping reverse fault models. This finding is inconsistent with what had been found before. Here, based on the geomorphological analysis of the epicentral area and the interpretation of the deformation field, we assume that coseismic slip occurred on complex faults consist of a forward and a backward thrust fault. Our inversion results indicate that the first mainshock occurred on a N dipping thrust fault with near east-west orentiation located between Namak and Handun anticlines, and the second mainshock occurred north of Handun anticline along a S-dipping thrust fault oriented W-E, produced most of the subsidence deformation in the south of epicenter. The scalar seismic moments released by the twin shocks from our analysis are equivalent to M_w6.45 and M_w6.10, which are consistent with the moment magnitudes reported by USGS and GCMT, respectively. The Coulomb stress analysis based on the slip distributions of the first mainshock reveals a trigger for the second event. The faulting mechanism of the doublet earthquakes suggests that anticlines and synclines in this area may play a more important role in controlling the way to release of accumulated stress caused by the long-term convergence of the Arabian Plate with the Eurasian Plate and local folding or faulting.