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Imaging the South American Active Margin and Continental Interior with Waveform Tomography

Session: Subduction Processes Along Latin America Subduction Zones [Poster]

Type: Poster

Date: 4/19/2021

Presentation Time: 11:30 AM Pacific

Description: 

The Andean margin is a long-lived, continuous subduction zone, considered an archetypal example of the subduction of an oceanic plate beneath a continent. However, the complex system shows profound changes north-south along the trench and is far from steady-state; its structure and dynamics are widely debated. Diverse deformational styles, topographic changes, irregular seismicity and volcanism are indications of the heterogeneity of the structure of the subduction in depth.

Seismic tomography can resolve the 3D distribution of seismic-wave velocity, sensitive to temperature and composition in the crust and upper mantle. Until recently, seismic data sampling in South America was highly uneven, and high-resolution models were obtained mainly regionally. Here, we assembled all now available seismic data including the recently collected data from the FAPESP “3-Basins Thematic Project.” The massive dataset includes data from the temporary deployments in South America that became available recently and is complemented by data from all the globe.

Our high-resolution, S-velocity tomographic model of South America and surrounding oceans is computed using the Automated Multimode Inversion of surface, S- and multiple S-waves. Our model has the data sampling to resolve regional-scale features such as the underthrusting of the Brazilian lithosphere beneath the Andes, slab stagnation in the transition zone, and slab windows in the upper mantle. We separate, for the first time, two different structures in the Northern Andes that are likely to represent two separate subducting slabs, relating to the Nazca and Caribbean Plates. In the Peruvian region, we image a very heterogeneous, ~800 km long flat slab with irregular topography. In the stable platform, we image in detail the lateral extent and internal structure of the cratons that comprise the ancient core of the continent. Accurate imaging of the structure of the downgoing Nazca slab and the continent’s lithosphere yields new insights into the evolution of South America and deformational processes involved in the cordillera build up.

Presenting Author: Bruna Chagas de Melo

Student Presenter: Yes

Authors