  We perform an adjoint waveform tomography using Rayleigh wave Empirical
Green's Functions (EGFs) at 10-50 s periods to improve a prior 3-D 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 travel-time misfits between the synthetic Green's Functions
(SGFs) and EGFs measured in different period bands. The total misfit is dropped
by ~75 percent after 6 iterations. Overall, the adjoint tomography provides
images with more realistic and improved resolutions and amplitudes due to the
inclusion of finite-frequency waveforms. The use of a numerical
spectral-element solver in adjoint tomography provides highly precise
structural sensitivity kernels, resulting in more robust images compared to
those generated by ray-theory tomography. Our study also demonstrates
improvement in lateral resolution and depth sensitivity. The final model
adjusts the shapes of velocity anomalies at crustal and uppermost mantle depths
especially in the Zagros convergence zone. These improvements include a
high-resolution image of delamination of the subducting Arabian lithosphere
from Zagros lower crust beneath the central and NW Zagros. The refine,
high-resolution images also better show the geometry of low-velocity anomalies,
which represent diachronous underthrusting of Arabian crust beneath central
Iran.
