Slab Rollback Orogeny Model: A Test of Concept.

Buoyancy forces associated with subducting lithosphere control the dynamics of convergent margins. In the postcollisional stage these forces are significantly reduced, yet mountain building and seismicity are ongoing, albeit at lower rates. We leverage advances of a newly developed seismo‐thermo‐mechanical modeling approach to simulate tectonic and seismicity processes in a self‐driven subduction and continental collision setting. We demonstrate that the rearrangement of forces due to slab breakoff, in the postcollisional stage, causes bending and rollback of the residual slab, suction forces, and mantle traction at the base of the upper plate, while stress coupling transfers to the shallow crust. Our results provide an explanation for the postcollisional evolution of the Central Alps, where the so‐called Slab Rollback Orogeny model explains the slow yet persistent upper plate advance, the height of the mountain range, and a seismicity pattern consistent with the different tectonic regimes throughout the orogen. Plain Language Summary: A long‐standing debate in tectonophysics evolves around whether vertical or horizontal forces are the primary drivers of mountain building processes. Here we explore this problem using 2‐D numerical models in a generic subduction and continental collision setting. Our results show how the postcollisional evolution of the orogen is controlled by a slow, but persistent, sinking and bending of the postbreakoff residual slab. The resulting seismicity pattern shows a broad pattern of different style of faulting, which are consistent with the local tectonic regimes. We find good correlations between our numerical results and the previously conflicting tectonic observations in the Central Alps and the adjacent foreland basin. Our results thus support the hypothesis that the postbreakoff remaining slab exerts a first‐order control on the motions and deformations of collisional orogens. Key Points: Two‐dimensional seismo‐thermo‐mechanical modeling is performed to investigate the driving forces during the postcollisional stagesPost‐breakoff residual slab proves sufficient to sustain slab rollback and retreat of the entire orogenThe proposed scenario is consistent with the postcollisional seismotectonic evolution of the central European Alps [ABSTRACT FROM AUTHOR]