Thesis Defense
Student: Israel Augusto Dragone
Program: Geophysics
Title: “A study of the velocity structures under the Paraná, Chaco-Paraná and Pantanal basins”
Advisor: Prof. Dr. Marcelo Belantani de Bianchi
Judging Committee:
- Prof. Dr. Marcelo Belentani de Bianchi - IAG/USP
- Prof. Dr. Marcelo Sousa de Assumpção - IAG/USP
- Prof. Dr. Marcelo Peres Rocha - UnB
- Prof. Dr. Cristobal Condori Quispe – UNSA
- Dr. Gabriel Negrucci Dragone – IAG/USP
Abstract
This work presents a travel time tomography for P- waves in the region of the Paraná, Chaco-Paraná e Pantanal basins using an independent and concise catalog combining local, regional and, teleseismic events. We develop a tool to quantify and filter the dataset using the correlation coefficient between the seismograms. In the inversion step, we used software with fewer geometry limitations to allow the tree datasets to be joined. We perform several synthetic tests and ray density evaluations to understand the model resolution and reliability. In general the final resolution for the anomalies in upper mantle region was of 250 km. On the first 100 km, we observed low-velocity anomalies that were geographically correlated to Upper Cretaceous alkaline intrusions and zones that suffered lithospheric thinning. We compare the contour of the proposed cratonic blocks with our results at 100 km depth. The vertical sections show the Nazca plate suffers depth variation from north to south, being stagnant on the base, or right below, the mantle transition zone, between 600 and 800 km, in the Peruvian flat slab region. We also map the plate continuity up to 1 500 km toward the easter of the continental coast and observe gaps in the plate. Plate continuity to the North is still a challenge due to low rays coverage.
Keywords: Seismic tomograph, intracratonic basins, Nazca subduction