Browsing by Autor "Gonzalo A. Fernandez"

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    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
    (Wiley, 2019) Carolina Rivadeneyra‐Vera; Marcelo Bianchi; Marcelo Assumpção; Victoria M.A.S. Cedraz; Jordi Julià; Martín Caeiro Rodríguez; Leda Sánchez Bettucci; Gerardo Sánchez; Luciana Lopez‐Murua; Gonzalo A. Fernandez
    Abstract 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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    Unveiling midcrustal seismic activity at the front of the Bolivian altiplano, Cochabamba region
    (2025) Gonzalo A. Fernandez; Benoît Derode; Laurent Bollinger; Bertrand Delouis; Mayra Nieto; Felipe Condori; Nathan Sarret; Jean Letort; S. Godey; M. E. P. E. P. Wimez
    Located in the heart of the Bolivian orocline, the Cochabamba department and its two million inhabitants are exposed to frequent seismic activity. However, the tectonic structures causing these earthquakes remain poorly identified. Indeed, Bolivia’s national seismological network does not optimally cover the area and the hypocentral locations of local earthquakes are therefore subject to large uncertainties which hinder their association with specific faults. We established a regional network consisting of 11 broadband and short-period seismic stations, spaced approximately 20 km apart. This study highlights the initial 6-month seismic bulletin made by manual and automated deep-neural-network based seismic phase picking. We also test the network's ability to resolve focal mechanisms of moderate to small events with a combined inversion of waveforms and polarities. Our preliminary results document midcrustal microseismicity located in the Main Thrust fault shear zone, and in its hangingwall, in a region affected by tectonic slivers and transverse faults impacting the sedimentary cover. These outcomes provide fresh insights into the fault system’s seismogenic behavior and potential across the Bolivian orocline.
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    Unveiling midcrustal seismic activity at the front of the bolivian altiplano, Cochabamba region.
    (2024) Gonzalo A. Fernandez; Benoît Derode; Laurent Bollinger; Bertrand Delouis; M. Nieto; Felipe Condori; Nathan Sarret; Jean Letort; S. Godey; M. E. P. E. P. Wimez