Flat slab deformation caused by interplate suction force

Abstract

We image the structure at the southern end of the Peruvian flat subduction zone, using receiver function and surface wave methods. The Nazca slab subducts to ∼100 km depth and then remains flat for ∼300 km distance before it resumes the dipping subduction. The flat slab closely follows the topography of the continental Moho above, indicating a strong suction force between the slab and the overriding plate. A high-velocity mantle wedge exists above the initial half of the flat slab, and the velocity resumes to normal values before the slab steepens again, indicating the resumption of dehydration and ecologitization. Two prominent midcrust structures are revealed in the 70 km thick crust under the Central Andes: molten rocks beneath the Western Cordillera and the underthrusting Brazilian Shield beneath the Eastern Cordillera.