Zagros collision zone was formed by collision between the Arabian plate and central Iranian micro-continent. The Zagros belt is important in terms of one of the youngest and most active continental collisions while interactions with its deformation zone continues. In order to study the crustal structure across the northern part of the Zagros collision zone, we process continuous vertical-component seismograms recorded by ~85 broad-band stations situated in the east of Iraq, Zagros Mountains, Central Iran and western Alborz (Figure 1-a). To estimate the inter-station Green functions by crosscorrelation, we employed a method described by Bensen et al. (2007). A multiple-filter analysis technique (e.g., Dziewonski et al., 1969) was employed to visually determine both the group and phase velocities of fundamental mode Rayleigh waves between periods of 5 and 35 s. To construct the phase and group velocity maps, we used the twodimensional technique developed by Ditmar and Yanovskaya (1987). The phase and group velocity maps with a lateral resolution of ∼ 60 km for most of the study region were generated. To constructed 1-D velocity model to Rayleigh phase and group dispersion curves, a
Bayesian Monte-Carlo algorithm (Manu-Marfo et al., 2019) was applied on 0.3° × 0.3°geographic grids. Juxtaposing the all shallow 1D models generated by inversion of noise tomographies, we composed a 3D velocity model for the study region which is the first high resolution crustal image beneath the Zagros collision zone. 3-D model reveals a shallow (< 15 km) low velocity anomaly beneath the Zagros Mountains (Figure 2) consistent with the geology. It is almost known that the Zagros was covered by a thick sedimentary layer (~ 10 km). Similar shallow low velocity anomaly is observed beneath Central Iran in section A-A' (Figure 2-a) where thick sedimentary layer was reported before by geology (Teknik and Ghods, 2017). The shallow high velocity anomaly is a continuous suture-parallel feature observable beneath the most of the SSZ as it is shown in the vertical sections A-A' and B-B' (Figure 2). The most prominent shallow feature observed in the 3D velocity model is the mid-crustal low velocity (Vs ~ 3.2 km/s) layer beneath the Zagros Mountains at depth between 20 km and 30 km. This low velocity layer looks like the mid-crustal low velocity layer beneath Tibetan plateau (Klemperer, 2006 and references therein) generated by a crustal channel flow.