← Back to Sessions

Physical Properties of the Mantle Beneath Patagonia From Surface and Body Wave Tomography

Description: 

The subduction of the Chile Spreading Ridge beneath South America 12-16 Myr ago opened a gap in the subducting slab beneath southern Patagonia. Paleo-reconstructions show a northward migration of the Chile Triple Junction to its present location around 46^oS, but structure anomalies and geodynamic processes associated with the slab window have been poorly understood. The recent deployment of broadband seismic instruments in Patagonia by the GUANACO experiment (2018-2021) and the Chilean National Seismic Network present an opportunity to image the slab window and associated structures in more detail. Here, we will discuss first our recent Vsv model using receiver functions, ambient seismic noise, and earthquake Rayleigh waves showed a thinning of the lithosphere between 46^oS and 49^oS as a consequence of thermal erosion induced by the slab window (Mark et al, 2022). Then we will discuss our recent seismic anisotropy results constraining mantle flow beneath Patagonia (Ben-Mansour et al., 2022). Using shear wave splitting analysis, we observe strong splitting of up to 2.5 s with an E-W fast direction just south of the triple junction and the edge of the subducting Nazca slab. This region of strong anisotropy is coincident with low uppermost mantle shear velocities implying an absence of mantle lithosphere. This indicates that the mantle flow occurs in a warm, low-viscosity, 200-300 km wide shallow mantle channel just to the south of the Nazca slab. Finally, we will show the latest results of our body wave finite-frequency tomography that provide adding information on the the geometry of the subducted slab, the extent of the slab window, and the mantle dynamics associated with slab window formation.

Session: Subduction Zone Structure From Trench to Arc

Type: Oral

Date: 4/19/2023

Presentation Time: 11:30 AM (local time)

Presenting Author: Walid Ben Mansour

Student Presenter: No

Invited Presentation: 

Authors