The Dynamics of the India‐Eurasia Collision: Faulted Viscous Continuum Models Constrained by High‐Resolution Sentinel‐1 InSAR and GNSS Velocities.

The distribution and magnitude of forces driving lithospheric deformation in the India‐Eurasia collision zone have been debated over many decades. Here we test a two‐dimensional (2‐D) Thin Viscous Shell approach that has been adapted to explicitly account for displacement on major faults and investigate the impact of lateral variations in depth‐averaged lithospheric strength. We present a suite of dynamic models to explain the key features from new high‐resolution Sentinel‐1 Interferometric Synthetic Aperture Radar as well as Global Navigation Satellite System velocities. Comparisons between calculated and geodetically observed velocity and strain rate fields indicate: (a) internal buoyancy forces from Gravitational Potential Energy acting on a relatively weak region of highest topography (>2,000 m) contribute to dilatation of the high plateau and contraction on the margins; (b) a weak central Tibetan Plateau (∼1021 Pa s compared to far‐field depth‐averaged effective viscosity of at least 1022–1023 Pa s) is required to explain the observed long‐wavelength eastward velocity variation; (c) localized displacement on fault systems enables strain concentration and clockwise rotation around the Eastern Himalayan Syntaxis. We discuss the tectonic implications for rheology of the lithosphere, distribution of geodetic strain, and partitioning of active faulting and seismicity. Plain Language Summary: The collision of the Indian Plate with Eurasia has created the Tibetan Plateau, one of the largest deforming regions in the continents. The mode of deformation has been a focus for heated debate and has inspired two contrasting tectonic models: (a) The deformation is localized on major faults separating "blocks" or (b) the strain is distributed throughout a "continuum." We approximate the India‐Eurasia collision by treating the continent as a thin viscous shell with regional variations in strength, explicitly accounting for displacements on selected major faults. We present a suite of models to explain the key features of new geodetic measurements from satellites. The best‐fit model involves a weak Tibetan Plateau, a particularly weaker central plateau, and four strong regions outside the plateau, and allows displacements on major faults. This represents the deformation field of the India‐Eurasia collision zone as a combination of continuous distributed deformation and focused strain on major faults. Key Points: A suite of faulted viscous shell models testing key parameters explain new observations from geodesy for the India‐Asia collisionThe India‐Asia collision is explained by the balance between buoyancy and boundary forces, slip on faults, and internal strength variationsCentral Tibetan Plateau has a vertically‐averaged effective viscosity of ∼1021 Pa s, 1–2 orders lower than the surrounding area [ABSTRACT FROM AUTHOR]