Segmented Crust of Southeastern Iran Reveals Complex Dynamics of the Zagros–Makran Transition: Insights From Ambient Noise Full‐Waveform Inversion

Abstract Southeastern Iran represents a key tectonic transition between the Zagros continental collision belt and the Makran oceanic subduction zone, providing an important natural setting to investigate how crustal structure and slab geometry vary across a collision–subduction boundary. Using a newly acquired seismic data set and an ambient noise full‐waveform inversion method, we obtain a high‐resolution 3D shear‐wave (S‐wave) velocity model for the crust and uppermost mantle down to 60 km depth. The obtained velocity structure is highly heterogeneous and exhibits pronounced segmentation. Makran is characterized by low‐angle (∼8°–10°) oceanic subduction, while Zagros is dominated by pronounced collision‐related crustal thickening and prominent low‐velocity shear zones. The deepest Moho reaches ∼55 km depth beneath the Urumieh Dokhtar Magmatic Arc (UDMA), while the thinnest crust of ∼35 km (including sediments) is observed near Coastal Makran. Extremely thick, low‐velocity sedimentary packages are imaged beneath the Makran accretionary wedge (∼20 km) and the Zagros fold‐thrust belt (∼15 km). A mid‐crustal high‐velocity anomaly observed beneath the southern UDMA indicates solidified magmatic rocks. Another high‐velocity anomaly beneath the Jaz Murian basin is interpreted as remnant oceanic lithosphere. A prominent lateral velocity contrast in the lower crust and uppermost mantle at the Zagros–Makran boundary, along with a diffuse zone in the middle‐upper crust, indicates depth‐dependent segmentation across this transition. These new constraints on slab geometry and crustal architecture refine our knowledge of the evolution of the Arabia–Iran convergent margin.