We apply adjoint waveform tomography using Rayleigh wave Empirical Green's Functions (EGFs) at 10-50 sec. periods to improve a prior 3D velocity model of the crust and uppermost mantle beneath the Iranian Plateau. EGFs were derived from cross-correlations of ~8 years of continuous vertical component seismic noise recorded by 119 broadband stations within the region. Adjoint tomography refines the initial model by iteratively minimizing the frequency-dependent traveltime misfits between the Synthetic Green's Functions (SGFs) and EGFs measured in different period bands. The total misfit has dropped by ~85 percent after 12 iterations. The use of a numerical spectral-element solver enables highly accurate wavefield simulations and, by exploiting full-waveform information, yields precise adjoint misfit kernels, resulting in more robust images compared to ray-theory tomography. Our study also demonstrates improved lateral resolution and depth sensitivity relative to the initial model obtained from conventional ambient-noise tomography. The final model adjusts the shapes of velocity anomalies at crustal and uppermost mantle depths especially in the Zagros convergence zone. Using a more limited dataset than some previous regional tomographic studies, the refined model captures along-strike variations in Arabian underthrusting beneath Central Iran, illustrating the potential of adjoint noise tomography to recover meaningful crustal-scale structural features.
Komeazi et al. (Fri,) studied this question.