The improved Moho depth imaging in the Arabia-Eurasia collision zone: A machine learning approach integrating seismic observations and satellite gravity data

Abstract

The Arabia-Eurasia convergences created one of the earth's topographic highs on the Central Tethys collisional belt. Despite the area's geological significance, a comprehensive and high-resolution map of Moho depth has been lacking due to the sparse and uneven distribution of seismically constrained Moho depth data. This study addresses this deficiency by compiling an extensive dataset of nearly 2500 seismically measured Moho depth points from 68 seismic local scale studies, resulting in the development of an updated seismically constrained Moho depth model (S-Moho) at a 0.5° × 0.5° spatial resolution. Despite some coverage gaps in the remote areas, the S-Moho model offers a more detailed view than previously available. To further improve the coverage of the S-Moho depth model, an incremental data-driven approach was employed. Initially, a gravity-based regression Moho depth model (SB-Moho) was developed by correlating S-Moho depth points with corresponding Bouguer anomalies. However, its accuracy was constrained by unaccounted isostatic and non-isostatic components. To address this limitation, a sliding window approach was applied to derive a windowed SB-Moho model (WSB-Moho). Additionally, a machine learning-based Moho model (ML-Moho) was developed using seismic Moho depth points along with 11 predictive variables. Both WSB-Moho and ML-Moho models demonstrated consistent and smooth Moho depth variations. The Zagros region reveals a prominent NW-SE oriented Moho depression (45-60 km thick), attributed to the underthrusting of the Arabian Plate beneath the Iranian Plateau. The models suggest that crustal thickening extends beyond tectonic boundaries, likely influenced by the dip of suture zones. In contrast, the crustal thickening in eastern Anatolia, northwest of the Zagros, is less pronounced, indicating different geodynamic processes. Strike-slip faulting and magmatic activity in this area contribute to a broader distribution of deformation compared to the more localized crustal thickening in the Zagros. In southeastern Zagros, strike-slip faults in central Iran accommodate much of the northward convergence of the Arabian Plate, thereby limiting the extent of crustal thickening.