Sallow crustal model of the DehDasht in Zagros, Iran, using classical Rayleigh wave tomography

Knowledge about the shallow crustal structure could provide an insight of local tectonic setting, stress filed and etc. which can be applicable in hazard assessment of infrastructures. The Arabian-Eurasian plates' convergence led to a compression zone in the south of Iran (Zagros) which is one of the most active collision zones. The salt-rich DehDasht structural embayment located in the central part of Zagros folded and thrust belt in the SW of Iran is an example of a complex geologic area. This region is characterized by high seismicity, hence by applying a dense network of stations, all faulting, anticlines structures, and also crustal model can be retrieved. Due to the complex geology of the study region and the presence of the great thickness of the sedimentary cover and several interbedding evaporitic deposits, we apply the surface wave tomography in studying the crustal structure of the DehDasht basin. In this regard, we processed more than 1000 micro-earthquakes recorded by 115 broadband stations in 9 months with the 100 sps. After selecting strict data selection criteria (SNR4, 3, 15km35km), the dispersion curves of Rayleigh waves (U; observed data) were then measured using the multiple filter analysis method. Afterward, an inversion stability condition (|U0-U|3 where represent the standard deviation of U at each period) were applied, and the tomography was done via applying the fast-marching method (FMST) for each period. A non-linear iterative damped least squares inversion procedure was then applied for each local dispersion curves to obtain 1D VS model up to 5 km of the crust beneath the DehDasht region. Finally, the inversion procedure was repeated separately for all cells, and these 1D shear velocity models were inserted into the original cells to construct a quasi-3D VS model. Our results represent well consistency with the tectonic structures of the region and are comparable to previous studies. The results pinpoint that a low velocity in the superficial can excite by thick sedimentary covers, while an abrupt transitions between regions of high- to low-velocity anomalies appear near the known faults and anticlines.