The Hindu Kush slab break-off as revealed by deep structure and crustal deformation
Sofia‐Katerina Kufner, Najibullah Kakar, Maximiliano Bezada, Wasja Bloch, Sabrina Metzger, Xiaohui Yuan, J. Mechie, Lothar Ratschbacher, S. Murodkulov, Zhiguo Deng, Bernd Schurr
Abstract
Break-off of part of the down-going plate during continental collision occurs due to tensile stresses built-up between the deep and shallow slab, for which buoyancy is increased because of continental-crust subduction. Break-off governs the subsequent orogenic evolution but real-time observations are rare as it happens over geologically short times. Here we present a finite-frequency tomography, based on jointly inverted local and remote earthquakes, for the Hindu Kush in Afghanistan, where slab break-off is ongoing. We interpret our results as crustal subduction on top of a northwards-subducting Indian lithospheric slab, whose penetration depth increases along-strike while thinning and steepening. This implies that break-off is propagating laterally and that the highest lithospheric stretching rates occur during the final pinching-off. In the Hindu Kush crust, earthquakes and geodetic data show a transition from focused to distributed deformation, which we relate to a variable degree of crust-mantle coupling presumably associated with break-off at depth.