Lithospheric structure of the Parana, Chaco-Parana, and Pantanal basins: Insights from ambient noise and earthquake-based surface wave tomography

Author(s)

Moura, Denise S. ; Nascimento, Andre V. S. ; Marangoni, Yara R. ; Chaves, Carlos A. M. ; Franca, George S.

• Document type: Journal article
• Source: Journal of South American Earth Sciences; v. 145, p. 18-pg., 2024-08-02.

Abstract

To investigate the lithospheric seismic structure of southern South America beneath the Parana<acute accent>, Chaco-Parana<acute accent>, and Pantanal basins, we measure two distinct sets of dispersion curves of Rayleigh waves: the first corresponds to 25,986 phase velocity dispersion curves in the period range 5-50 s, extracted from cross-correlation of the ambient noise between pairs of stations and thus sensitive mainly to crustal structure; the second set is derived from group velocities extracted from earthquake recordings, resulting in 33,888 dispersion curves with periods ranging from 8 to 200 s, allowing us to probe deeper Earth structure. From these data sets, we derive two independent S-wave velocity models following a two-step inversion procedure, resulting in a crustal and a lithospheric mantle model with depths extending up to 50 and 200 km, respectively. Features imaged in our crustal model include low velocity anomalies in agreement with the surface position of the major sedimentary basins and high velocity anomalies within fold-thrust provinces and the basement of the Pantanal basin. In the uppermost mantle, we identify high velocities in the region of the Parana<acute accent> basin, Sao Francisco and Amazonian cratons, and Luiz Alves block, and a low velocity feature beneath the Pantanal basin, which suggests a potentially thinner lithosphere under the basin. We also illuminate a strong velocity gradient boundary between the eastern border of the Pantanal basin with the Parana<acute accent> basin, from crustal to lithospheric mantle depths, which seems to delineate the western and southern borders of the Parana<acute accent> basin, coinciding with the Western Parana<acute accent> Suture. Additionally, we construct a Moho depth proxy map for the study area, which has an overall good agreement with previous results, except for a thicker crust beneath the southern Chaco-Parana<acute accent> basin. This area, together with a thicker crust counterpart in the Parana<acute accent> basin, has a remarkable correlation with the position of a volcanic layer related to the Parana<acute accent> Magmatic Province, which leads us to suggest that magmatic processes played an important role in the south Chaco-Parana<acute accent> basin as well. (AU)

• FAPESP's process: 22/04357-0 - Sequential inversion of surface wave dispersion curves and geoid anomalies integrated to shear wave splitting analysis: new constraints on the velocity, attenuation, density, and anisotropy structures of the crust and upper mantle beneath South America
• Grantee: Carlos Alberto Moreno Chaves
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/19562-2 - Study of physical and structural properties in the region of the Pantanal, Paraná and Chaco-Paraná basins using joint inversion of gravimetric observations and surface waves velocity
• Grantee: Denise Silva de Moura
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 13/24215-6 - Pantanal-Chaco-Paraná basins (PCPB): crust and upper mantle seismic structure and evolution
• Grantee: Marcelo Sousa de Assumpção
• Support Opportunities: Research Projects - Thematic Grants