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The closure of an ancient ocean basin via oceanic arc‐continent collision has two subduction styles with opposite polarities, which may proceed via subduction polarity reversal (SPR) or a subduction zone jump (SZJ). Interpreting the geometry or kinematic evolution of ancient collisional zones, especially the original subduction polarity, can be challenging. Here we used 2D thermo‐mechanical modeling to investigate the dynamic evolution process of SPR versus SZJ. Our modeling predicts different structural, topographic, magmatic, and basin histories for SPR and SZJ, which can be compared against, and help interpret, the geologic record past sites of oceanic closure during collisional orogens. Our results match geologic observations of past collisions in Kamchatka, eastern Russia, and the Banda Arc, eastern Indonesia, and thus our results can help effectively decode the evolutionary history of past arc‐continent collisions. Plain Language Summary: Determining the geometry and kinematic evolution of ancient subduction zones that experienced collision with an oceanic island arc can be challenging based on the surface geology along. Such collisions usually result in different dynamical evolution processes, namely subduction polarity reversal (SPR) or a subduction zone jump (SZJ). Here we conducted numerical modeling of oceanic island arcs that collide with a continental margin to explore the dynamic evolution process of different subduction styles. Our results reveal geologic indicators to decipher SPR versus SZJ in natural oceanic arc‐continent collisions, such as the distribution of thrust faults, metamorphic rocks, magmatism, crustal thickness, and topography. The numerical simulations help explain the geologic history of Kamchatka in eastern Russia and Banda Arc in eastern Indonesia. This study provides provide new insights and implications diagnosing the polarity of vanished subduction in arc‐continental systems. Key Points: New numerical models with convergent velocity boundary condition for deciphering subduction polarity during arc‐continent collisionsThrust faults, metamorphic rocks, magmatism, topography and Moho morphology can be used as indicators to diagnose subduction polarityThe evolution of subduction polarity reversal well explains the tectonic activities of the Kamchatka and Banda Arc in the Cenozoic [ABSTRACT FROM AUTHOR]

We investigated velocity and anisotropic structure of the crust beneath the eastern margin of the Tibetan Plateau to better understand its deformation and evolution mechanism. We performed H‐κ and Pms anisotropy analyses to obtain crustal thickness, Vp/Vs ratio, fast polarization direction, and splitting time from 711 stations, and further conducted quality control using slowness, harmonic and statistical analyses. The Songpan‐Ganzi Block has a large splitting time and a fast polarization direction roughly parallel to the GPS motion and SKS fast direction. It also shows an overall high but complex distribution of Vp/Vs ratio, and large variations in crustal thickness, indicating that crustal deformation is likely caused by crustal shortening and lower crustal flow. The northern Sichuan‐Yunnan Rhombic Block (SYRB) is featured by a thick crust and high Vp/Vs ratio, suggesting that the crust is likely inflated by partial melting lower crustal rocks. The subblock also exhibits a strong azimuthal anisotropy with a splitting time greater than 0.6 s. The fast polarization direction aligns with the nearly N‐S extended direction and rotates clockwise in front of the Emeishan Large Igneous Province (ELIP). The observed anisotropy agrees with aligned amphibole minerals under a simple shear condition, supporting a southward lower crust flow being diverted by the ELIP. Anisotropy measurements on the southern SYRB are less robust and widely scattered, suggesting a deformation mechanism different from the northern SYRB. In addition, the southeastern margin of the Sichuan Basin shows a systematic pattern of crustal anisotropy consistent with a pure shear deformation mechanism. Plain Language Summary: We studied the crustal structure and deformation beneath the eastern edge of the Tibetan Plateau. By analyzing teleseismic data from 727 stations, we measured crust thickness, Vp/Vs ratio, and azimuthal anisotropy using receiver functions. Our findings show a complex crustal behavior pattern in the eastern Tibet margin. In the Songpan‐Ganzi Block, crustal shortening and lower crust flow seem to be causing deformation. The northern Sichuan‐Yunnan Rhombic Block, with its thick crust and high Vp/Vs ratio, appears to be influenced by partial melting of lower crust rocks. And a southward lower crust flow being diverted by the Emeishan Large Igneous Province. The eastern and southern part of this block shows a different pattern, indicating a unique deformation mechanism. Additionally, the southeastern margin of the Sichuan Basin appears to undergo a distinct type of crustal deformation. Key Points: A new crustal model with much more reliable and denser Pms anisotropic measurements is built in the eastern Tibetan MarginSongpan‐Ganzi Block is likely deformed by crustal shortening and lower crustal flowChannel flow may exist in the west low velocity zone (LVZ) while absent at the east LVZ [ABSTRACT FROM AUTHOR]

Competing Interests: Conflict of Interest The authors declare that they have no competing interests.