Luca Dal Zilio, Edi Kissling, Taras Gerya, Ylona van Dinther

Forces associated with subduction of cold and dense oceanic plates control the motions and deformations of convergent margins. However, how these forces sustain mountain building processes — especially after slab breakoff — is still poorly known. Here we investigate this conundrum by performing 2-D, visco-elasto-plastic, seismo-thermo-mechanical numerical modeling, which simulates both tectonic and seismicity processes in a subduction and continental collision setting. Results reproduce the self-driven stages of subduction, continental collision, and spontaneous slab breakoff. The subsequent evolution of the orogen shows how slow, but persistent, flexural bending of post-breakoff residual slab and crustal delamination control the post-collisional evolution of the orogen. This so-called Slab Rollback Orogeny model leads to bending-related slab suction, nappe stacking of the crustal root, widening of the orogen, and a seismicity pattern consistent with the different tectonic regimes throughout the orogen. Our results provide an explanation for the post-collisional evolution of the Central Alps and its current seismicity.