Abstract
Inaugurated in 2006, the Irape Hydroelectric Plant has the highest dam in Brazil, with 210 m. The Seismological Observatory of the University of Brasilia is monitoring this structure since the beginning of its reservoir filling. The reservoir triggered seismicity caused by the increase of crustal tension just after the start of the remains like an important object of study for understanding this phenomenon. This paper aims at studying the seismicity recorded from January to May 2006, as well as to characterize the geology around the Hydroelectric Plant Irape in order to identify and describe the structures that help for better understanding the seismic events. The spatial orientation of the seismic events obtained by analyzing polarity and waveform is consistent with the guidance of prominent relief lineaments. These faults can be found attached to a larger structure with main NE/SW direction and tens of kilometers, which would be responsible for capturing Jequitinhonha and Aracuai rivers. This great lineament is interpreted herein as a structure related to a late stage of the Brasiliano-Panafrican event. The solution of focal mechanism, created using an inversion method of the waveform in the time domain, indicates that the direction of the possible plans are correlated to main failure of brittle structures targeting the area of work.
Highlights
PALAVRAS-CHAVE: reativação sísmica de estruturas geológicas; estudos de sismicidade desencadeada por reservatório; Usina Hidrelétrica de Irapé
Inaugurated in 2006, the Irapé Hydroelectric Plant has the highest dam in Brazil, with 210 m
The reservoir triggered seismicity caused by the increase of crustal tension just after the start of the remains like an important object of study for understanding this phenomenon
Summary
A sismicidade desencadeada por reservatório (SDR) é um fenômeno com influência antropogênica registrado concomitantemente e/ou posteriormente ao preenchimento de um reservatório de água (geralmente uma usina hidrelétrica – UHE), em que anteriormente havia, ou não, o registro de atividade sísmica (Simpson 1976; 1986). Apesar de este fenômeno ser recorrente em diversas barragens brasileiras e no mundo, há certa carência de estudos que verifiquem a natureza das estruturas geológicas causadoras dos sismos e a correlação destes com a estruturação pretérita impressa nas rochas. Segundo Chimpliganond et al (2007), os quais primeiramente estudaram estes eventos, a UHE de Irapé apresenta sismicidade do tipo inicial, com o primeiro evento sísmico sendo registrado após o começo do enchimento do reservatório em um período de dias (Fig. 1). O objetivo deste trabalho foi identificar, descrever e verificar a correlação entre as estruturas geológicas e a localização e as características dos eventos sísmicos desencadeados por um reservatório na UHE de Irapé, conferindo a hipótese de que falhas preexistentes podem ser reativadas pela mudança de direção e intensidade no campo de tensões locais, gerando os eventos de SDR
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