Middle‐Lower Crustal Deformation Drives Differential Vertical Motion Along the Western Margin of the Ordos Block: Constraints From Full‐Waveform Inversion

The mechanism of localized rapid uplift in the northeastern Tibetan Plateau remains elusive to date. Here, we apply full‐waveform inversion to investigate the crustal deformation that links plateau uplift to subsurface geodynamic processes during the lateral expansion of the northeastern Tibetan Plateau. By iteratively minimizing phase and amplitude differences between synthetic and observed seismograms, we reconstruct a 3D velocity model, FWWOB25, beneath the western margin of the Ordos Block and its adjacent regions to identify key tectonic units. The model reveals two disconnected intracrustal low‐velocity layers in the West Qinling Orogenic Belt and Longzhong Basin's middle‐lower crust, while a high‐velocity anomaly extends from the middle crust to the Moho at the Ordos Block's southwestern margin. The wedge‐shaped structures occur on both sides of this high‐velocity anomaly, accompanied by lower crustal thickening and crust‐mantle deformation decoupling. Combined with regional tectonics, the middle‐lower crust beneath the Longzhong Basin compresses the rigid Ordos Block, causing crustal shortening. Controlled by pre‐existing structure, the middle‐lower crustal deformation drives rapid uplift in the Ordos southwestern margin, while limited crustal deformation in the northwestern segment is associated with strike‐slip motion of the Haiyuan fault. The varying middle‐lower crustal deformation pattern in the two segments leads to different vertical motion. Other than confirming the critical role of middle‐lower crustal deformation that drives localized rapid surface uplift, our seismic imaging also clarifies the subsurface geodynamic processes that govern the expansion of the northeastern Tibetan Plateau into surrounding rigid blocks.