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Multi-Scale, Finite-Frequency Body Wave Tomography With Relative Kernels

Description: 

The subduction of the Chile Spreading Ridge beneath South America beginning 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 geographical extent of the slab window was previously inferred from the spatial distribution of magma composition and the analysis of seismic waveforms from temporary seismic arrays (2004-2006) near the Chile Triple Junction. 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 use teleseismic P and S wave travel time residuals to carry out finite-frequency tomography. We compute the travel time residuals in high frequency (0.3-1.5Hz) and low frequency (0.03-0.125 Hz) bands and invert them to P and S-wave 3D models taking advantage of the different finite-frequency kernels obtained from different frequency bands. Crustal corrections are determined from a recent regional scale shear velocity model of shallower structure derived from surface wave tomography and receiver functions [Mark et al, 2022]. Our new seismic models show the transition between the Nazca slab associated with fast upper mantle velocity anomalies and the slab window with slow velocity anomalies. The southern extent of the slab window and the presence of a thicker continental lithosphere observed beneath the Austral-Magallanes Basin are consistent with the recent surface wave tomography results. In this presentation, we will discuss the 3-D geometry of the subducted slab and the effect on the mantle flow pattern derived from shear wave splitting results [Ben-Mansour et al., 2022], the spatial distribution of volcanism (arc versus backarc regions) and the support of the present-day surface topography with a dynamic contribution from the mantle across Patagonia.

Session: Earth’s Structure from the Crust to the Core [Poster Session]

Type: Poster

Date: 5/2/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Walid

Student Presenter: No

Invited Presentation: 

Authors