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Master's Dissertation
DOI
https://doi.org/10.11606/D.14.2023.tde-31102023-172712
Document
Author
Full name
José Alexandre Araujo Nogueira
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2023
Supervisor
Committee
Assumpcao, Marcelo Sousa de (President)
Barros, Lucas Vieira
Carvalho, Juraci Mário de
Title in English
Relative Location of Regional Epicenters in Brazil and Source Parameters
Abstract in English
We employed cross-correlation analysis of P, S, and Lg-waves to accurately locate the aftershocks relative to a reference event. By analyzing the distribution of aftershocks in several cases, we were able to infer the source parameters like fault plane of the main earthquake, stress drop characteristics and provide constraints for the focal mechanism determination. The methodology involves two approaches that requires a reference event whose signals are cross-correlated with another event (target) to obtain relative travel times to a given regional network. This method assisted in estimating the source characteristics of four seismic Mainshock-aftershock sequences in intraplate region of Brazil. In general, all events were relocated near the mainshock. Specifically, the results show a NW-SE fault trend and thrust focal mechanism for Amargosa-BA (2018-2020) and Cajati-SP (2015-2020) sequences. The 1965 and 2021 earthquakes in Guyana did not originate from the same fault. The Sete Lagoas-MG (Apr-Dec/2022) sequence exhibited two possibilities: either independent fault planes or a SW-NE trend dipping to NW.
Title in Portuguese
Localização relativa de epicentros regionais e parâmetros da fonte
Keywords in Portuguese
Epicentro
Falha
Localização relativa
Mecanismo focal
Abstract in Portuguese
Utilizamos a análise de correlação cruzada das ondas P, S e Lg para localizar com precisão as réplicas de um terremoto em relação a um evento de referência. Ao analisar a distribuição das réplicas em diversos casos, pudemos inferir parâmetros da fonte, como o plano de falha do terremoto principal, estimar o \textit{stress drop} e fornecer restrições para a determinação do mecanismo focal. A metodologia envolve duas abordagens que requerem um sismo referência e um alvo, cujos sinais são correlacionados a fim de obter os tempos de percurso relativos para uma estação. Essa metodologia auxiliou na estimativa das características da fonte de quatro sequências de sismos na região intraplaca brasileira. De forma geral, todos os eventos foram relocados para mais próximos ao evento referência. Especificamente, os resultados mostram um padrão de falha NW-SE e um mecanismo focal reverso para as sequências de Amargosa-BA (2018-2020) e Cajati-SP (2015-2020). Os terremotos de 1965 e 2021 na Guiana não tiveram origem na mesma falha. A sequência de Sete Lagoas-MG (Abr-Dez/2022) apresentou duas possibilidades: ocorrência de sismos em planos independentes ou uma tendência SW-NE mergulhando para o NW.
 
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Publishing Date
2024-01-18
 
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