Crustal Architecture and Isostatic Support in Zagros and Central Iran: Evidence from Seismic and Gravity Analysis

This study investigates the crustal structure and lithospheric dynamics of the Zagros Mountains and Central Iran using a joint inversion of receiver functions and Rayleigh wave phase velocity dispersion for 19 seismic stations. The results reveal significant spatial variations in Moho depth and crustal thickness, reflecting the tectonic complexity of the region. Crustal thickness gradually increases from eastern Iran (∼40 km) to Central Iran (∼42 km) and reaches its maximum beneath the Sanandaj-Sirjan Zone (SSZ, ∼58 km) and the Urumieh-Dokhtar Magmatic Assemblage (UDAM, ∼52 km). This thickening is attributed to the underthrusting of the Arabian Plate beneath Central Iran and crustal shortening associated with the Zagros orogeny. Low shear-wave velocities (Vs < 4.1 km/s) observed in the uppermost mantle beneath Central and Eastern Iran indicate variations in lithospheric composition and thermal structure. Correlations between crustal thickness, topography, and free-air gravity anomalies demonstrate the role of isostatic support and lithospheric flexure in shaping regional surface features. Positive gravity anomalies in the southern Zagros are linked to crustal underthrusting, while high-density rocks in the SSZ and UDAM contribute to short-wavelength gravity highs. These findings enhance our understanding of the geodynamic evolution of the Zagros and Central Iranian tectonic domains, highlighting their distinct geological histories and ongoing tectonic interactions.