Resumen

ROSA, María Laura; COLLACO, Bruno; ASSUMPCAO, Marcelo  y  SABBIONE, Nora C. Seismic tomography of the Chaco-Paraná basin using surface waves. Geoacta [online]. 2015, vol.40, n.2, pp.1-10. ISSN 1852-7744.

We present the results of a study of surface-wave group velocity tomography, for the Chaco-Parana basin region. Previous surface waves analysis (e.g., Snokes and James; 1997, Feng et al., 2004, 2007) estimated Moho depth in the central Chaco basin and a low-velocity anomaly in the lithospheric mantle. However the seismic structure of the crust and upper mantle remains little characterized across the region due to the rather poor resolution, especially for the south region. The aim of this work is to improve the resolution for the Chaco-Paraná basin region using dispersion curves from regional earthquakes recorded at permanent and portable stations and inter-station dispersion curves derived from correlation of ambient noise, for a dataset of seismic noise recordings from permanent and local networks (BRASIS, INPRES) stations, achieving a better path coverage and a more uniform azimuthally distribution. A 2D group velocity tomographic inversion was performed obtaining maps that display improved resolution in northern Argentina and southern Brazil. A grid-search method was applied to estimate a crustal thickness model for the Chaco-Paraná basin. Estimates of the crustal thickness agree with the ~34 km found for CPUP station, the observed thin crust (less than 35 km) suggested by Assumpção et al., 2013 and the average crustal thickness (32-35 km) suggested by Snoke and James, 1997, Prezzi et al., 2009 and Dragone et al., 2012. Large crustal thickness variation is also observed between the Andean region and the Chaco-Parana basin and a deeper crust is found in the Paraná basin region compared with the Chaco-Paraná basin.

Palabras clave : Surface wave tomography; Group velocity; Crust; Chaco-Paraná basin.

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