Banca de QUALIFICAÇÃO: Guilherme Manno Penna Crepaldi Affonso

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : Guilherme Manno Penna Crepaldi Affonso
DATE: 24/02/2023
TIME: 14:00
LOCAL: Auditório do IG e Teams
TITLE:

Study of the Upper Mantle Beneath Brazil with Multiple Frequency Seismic Tomography using Adjoint Inversion of Relative Residuals and Amplitude Anomalie.

KEY WORDS:

São Francisco Craton; Paranapanema Block,;Borborema Province; Amazonian Craton;Parnaíba Basin;Seismicity.

PAGES: 85
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Geologia
SUMMARY:

Multiple Frequency Seismic Tomography has been applied to study the upper mantle beneath Brazil with remarkable success, replacing the traditional tomography based on ray theory. Previous studies focused on specific regions, the Amazonian Craton and the region of the Paraná, Chaco and Pantanal basin, not providing complete images of the whole of Brazil. The objective of this work is to study the upper mantle beneath Brazil, inverting travel time residuals for all the 233 stations installed between 2011 and 2022. Seismograms were processed for P and PKIKP phases at six central frequencies (0.03, 0.06, 0.13, 0.25, 0.5, 1 Hz), with the final database consisting of 82,358 relative residuals. Resolution tests showed better resolution between depths of 136 and 226 km. Such tests simulated the presence of cratons and showed that the model has good capacity to recover the horizontal limits of the structures. However, vertical resolution is deficient, with the anomalies being smeared beyond their original depths. In the model with real data, a high-velocity anomaly was observed in the Amazonian Craton region, not being possible to differentiate between its geochronological provinces due to the lack of stations. Under the Parnaíba Basin, three high-velocity anomalies were observed, interpreted as the Granja and Parnaíba blocks, with the northern one being interpreted as the São Luis Craton, characterized by being thinner, with the probable cause being the metasomatism suffered during its separation from the West African Craton. The Borborema Province was characterized by a low-velocity anomaly, with the possibility that a plume may be associated with a strong negative anomaly in its center. The São Francisco Craton was related to a high-velocity anomaly, with its limits presenting correlation with previous tomographic studies. High-velocity anomalies were observed beneath the Paraná, Chaco and Pantanal basins, consistent with the presence of three cratonic blocks. The main block beneath the Paraná Basin, the Paranapanema Block, presents separation from the São Francisco craton to the north. Its limits seem to extend further south to those obtained by previous studies. The Rio Apa Craton did not extend beneath the northern portion of the Pantanal Basin, as proposed by previous studies. The Luiz Alves craton presented reduced limits, more concentrated to the south, when compared to a previous tomographic study.

BANKING MEMBERS:
Externo ao Programa - 2156153 - ELDER YOKOYAMA
Interno - 1303786 - ELTON LUIZ DANTAS
Externo ao Programa - 1823156 - GIULIANO SANT ANNA MAROTTA
Presidente - 1704135 - MARCELO PERES ROCHA
Interna - 2341034 - ROBERTA MARY VIDOTTI