Showing papers by "Maximiliano Bezada published in 2021"

The Hindu Kush slab break-off as revealed by deep structure and crustal deformation.

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. Here, the authors document active slab break-off and the crustal response during continental collision under the Hindu Kush, a rarely observed process since it happens over geologically short time spans.

Evaluating Models for Lithospheric Loss and Intraplate Volcanism Beneath the Central Appalachian Mountains

Abstract: The eastern margin of North America has been shaped by a series of tectonic events including the Paleozoic Appalachian Orogeny and the breakup of Pangea during the Mesozoic. For the past ~200 Ma, e...

Caribbean Slab Segmentation Beneath Northwest South America Revealed by 3-D Finite Frequency Teleseismic P-Wave Tomography

Abstract: Flat slab subduction generally refers to slabs that extend nearly horizontally for some distance, sometimes hundreds of kilometers, in the upper mantle (Cahill & Isacks, 1992). We distinguish flat subduction from under-thrusting by noting that an under-thrusted slab remains in contact with the overriding plate and no asthenosphere material separates them (Pennington, 1981). Flat slab subduction zones comprise about 10% of all subduction zones and have several features in common, including: (1) Increased upper plate seismicity compared to steep subduction (Gutscher et al., 2000); (2) Orogenesis hundreds of kilometers from the Abstract The Caribbean plate subducts beneath northwest South America at a shallow angle due to a large igneous province that added up to 12 km of buoyant crust. The overriding plate lacks volcanism and exhibits Laramide-style uplifts over 500 km from the trench. Here, we illuminate the subduction structures through finite frequency teleseismic P-wave tomography and connect those structures to the Laramide-style deformation on the overriding plate. We use a new data set collected from the CaribbeanMérida Andes seismic experiment comprised of 65 temporary broadband stations integrated with permanent stations from the Colombian and Venezuelan national networks. We identify three segments of subducting Caribbean plate with one segment completely detached from the surface. The timing of the detachment aligns with other regional events, including the uplift of the Mérida Andes, about 10 Ma. Slab buoyancy post-detachment likely resulted in recoupling with the overriding plate, reactivation of Jurassicaged rift structures and subsequent uplift of the Mérida Andes. Mantle counterflow over the broken segment induced by rollback of the attached slab likely contributed to the uplift of the Mérida Andes. We conclude that the northern limit of subduction lies south of the Oca-Ancón fault, though the fault itself may be the surface expression of the boundary. The southern limit of subduction lies south of our study area.

Evidence for Stress Localization Caused by Lithospheric Heterogeneity from Seismic Attenuation

Abstract: The Wyoming Craton underwent tectonic modifications during the Laramide Orogeny, which resulted in a series of basement-cored uplifts that built the modern-day Rockies. The easternmost surface expr...