Crustal and upper mantle structure in the intracratonic Paraná Basin, SE Brazil, from surface wave dispersion using genetic algorithms

An, Meijian; Assumpção, Marcelo

doi:10.1016/j.jsames.2006.03.001

Cited by 37 publications

(25 citation statements)

References 36 publications

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“…Different from the extrapolated model 3SMAC [ Nataf and Richard , 1996], the Amazon basin, does not show an overall thinner crust than the shields north and south of it. Beneath the northern Paraná basin the Moho is deeper than the surrounding fold belts, a result well constrained by the receiver functions from França and Assumpção [2004] and from An and Assumpção [2006, 2004]. Interestingly, a similar thickening is suggested for the Parnaíba basin in NE Brazil.…”

Section: Resultssupporting

confidence: 56%

Upper mantle structure of South America from joint inversion of waveforms and fundamental mode group velocities of Rayleigh waves

2007

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A new tomographic S wave velocity model for the upper mantle beneath South America is presented. We developed and applied a new method of simultaneously inverting regional S and Rayleigh waveforms and fundamental mode Rayleigh wave group velocities, to better constrain upper mantle S velocity structure and Moho depth. We used ∼5700 Rayleigh wave group velocity dispersion curves and 1537 regional wave trains with paths principally passing through the South American continent. The joint inversion of this data set provided a new three‐dimensional (3‐D) upper mantle S velocity model and a Moho depth model for South America, which fits both the group velocity and regional waveform data sets well. New features of the final three‐dimensional (3‐D) S velocity and Moho depth model correlate well with known geotectonic units on a regional scale. The Moho depth ranges from 30 km in the central Chaco basin to 42 km beneath the Amazonian craton and 45–70 km beneath the orogenic Andean belt. The imaged S velocity indicates an average lithosphere thickness of around 160 km for the Amazonian craton. High velocities are imaged beneath the Amazon and part of the Paraná and Parnaíba basins down to about 150 km. Low to very low velocities are imaged beneath the central Andes and the Chaco, Pantanal, and northwestern Paraná basins.

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Section: Resultssupporting

confidence: 56%

Upper mantle structure of South America from joint inversion of waveforms and fundamental mode group velocities of Rayleigh waves

2007

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“…[8] In this study, we used the inter-station Love and Rayleigh phase velocities from An and Assumpção [2004] as the surface wave observation. To avoid the influence of lateral heterogeneity, we only selected the path POPB-PACB which did not show obvious lateral heterogeneity in the analysis of SWD [An and Assumpção, 2004] and RFs.…”

Section: Observation Inversion and Results: Paraná Basin Brazilmentioning

confidence: 99%

Multi‐objective inversion of surface waves and receiver functions by competent genetic algorithm applied to the crustal structure of the Paraná Basin, SE Brazil

Assumpção

2004

Geophysical Research Letters

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[1] Surface wave dispersion and receiver functions are sensitive to different, but dependent, seismic properties. Their joint inversion is multi-objective and can provide tight constraints on layer-interfaces and S-velocities. We used one of the competent genetic algorithms, Bayesian optimization algorithm, as the multi-objective inversion technique. Multi-objective criterion of receiver functions and surface wave dispersion can better constrain solutions than each separate objective. We applied this new method to data from three stations in the Paraná Basin, Brazil, and found S-velocity structure well-constrained down to 150 km depth. The inverted S-velocities in the lower crust are less than 3.8 km/s and are lower than in the surrounding foldbelts. Some indication of high velocities (Vs > 4 km/s) in the 5 -7 km lowermost crust is given by a Moho transition zone. This may suggest that possible underplating was not widespread in the Paraná basin. INDEX TERMS:3260 Mathematical Geophysics: Inverse theory; 7218 Seismology: Lithosphere and upper mantle; 7255 Seismology: Surface waves and free oscillations; KEYWORDS: multi-objective optimization, surface wave, receiver function, crustal structure, Brazil. Citation: An, M., and M. S. Assumpção (2004), Multiobjective inversion of surface waves and receiver functions by competent genetic algorithm applied to the crustal structure of the Paraná Basin, SE Brazil, Geophys. Res. Lett., 31, L05615,

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“…Gravity data show a NE‐SW trending Bouguer high along the central axis of the Paraná Basin (e.g., Dragone et al, ), which had been interpreted as due to magmatic underplating in the lower crust related to the extrusion process. However, attempts to detect an underplated lower crust by seismic methods (An & Assumpção, , ; Julià et al, ; Shirzad et al, ) have not identified significantly higher velocities beneath the Paraná Basin. Perhaps the high Bouguer anomalies are due to a higher density (and high velocity) lithospheric lid as proposed by Chaves et al () and Rocha et al ().…”

Section: Geological Settingmentioning

confidence: 99%

An Updated Crustal Thickness Map of Central South America Based on Receiver Function Measurements in the Region of the Chaco, Pantanal, and Paraná Basins, Southwestern Brazil

et al. 2019

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Previous compilation of crustal structure in South America had large unsampled areas including the thin crust in the Sub‐Andean lowlands, largely estimated by gravity data, and the sparsely sampled Amazon Craton. A deployment of 35 seismic stations in Brazil, Bolivia, Paraguay, Argentina, and Uruguay improved the coverage of the Pantanal Basin in Western Brazil, the intracratonic Paraná and the Chaco Basins. Crustal thicknesses and Vp/Vs ratios were estimated with a modified H‐k method by producing three stacked traces to enhance the three Moho conversions (the direct Ps and the two multiples Ppps and Ppss). This modified method gives lower uncertainties than previous studies and shows more regional consistency between nearby stations. The temporary stations and the Brazilian Network (RSBR) have characterized the crustal structure as follows. The Paraná Basin has a thick crust 40–45 km and average Vp/Vs ratio (1.71–1.77), while the Chaco Basin has a slightly thinner crust (35–40 km) and higher Vp/Vs ratio (1.75–1.79). This confirms the lack of widespread magmatic underplating in the Paraná Basin that could be related to the origin of the flood basalts during the South Atlantic opening. A belt of thin crust (30–35 km) with low Vp/Vs (<1.74) is confined to the eastern edge of the Pantanal Basin. Normal crust (38–43 km) is observed along the western edge of the Pantanal, from the southern part of the Amazon craton to the Rio Apa cratonic block. This study, combined with other published data, provides an updated crustal thickness map of South America.

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Crustal and upper mantle structure in the intracratonic Paraná Basin, SE Brazil, from surface wave dispersion using genetic algorithms

Cited by 37 publications

References 36 publications

Upper mantle structure of South America from joint inversion of waveforms and fundamental mode group velocities of Rayleigh waves

Upper mantle structure of South America from joint inversion of waveforms and fundamental mode group velocities of Rayleigh waves

Multi‐objective inversion of surface waves and receiver functions by competent genetic algorithm applied to the crustal structure of the Paraná Basin, SE Brazil

An Updated Crustal Thickness Map of Central South America Based on Receiver Function Measurements in the Region of the Chaco, Pantanal, and Paraná Basins, Southwestern Brazil

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