The role of Precambrian mylonitic belts and present-day stress field in the coseismic reactivation of the Pernambuco lineament, Brazil

Ferreira, Joaquim Mendes; Bezerra, Francisco H.R.; Sousa, Maria O.L.; Nascimento, Aderson F. do; Sá, Jaziel Martins; França, George Sand

doi:10.1016/j.tecto.2008.01.009

Cited by 86 publications

(44 citation statements)

References 58 publications

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“…Unlike the Pernambuco lineament, where earthquakes are due to reactivation of the main shear zone (Ferreira et al 2008), the Transbrasiliano lineament does not present a direct relationship with the recent earthquakes in the Meruoca granite. In addition, unlike the Palhano and Augusto Severo cases, where the seismicity is related to faults that cut across preexisting structures, the Meruoca seismicity is related to the northern scarp of the Boqueirão valley, a remarkable 10 km long and 3 km wide structure located center-south of the granite.…”

Section: Discussionmentioning

confidence: 80%

“…Active faults in Borborema Province are usually strike-slip and generate events of up to 5.2 m b . Seismicity is concentrated in the upper crust down to a depth of 12 km (Ferreira et al 1998(Ferreira et al , 2008. Stress fields studies using focal mechanisms, borehole breakouts, fault slip data, and inelastic strain recovery measurements, indicate that the region is under a strike-slip regime.…”

Section: Tectonic Features Of the Borborema Provincementioning

confidence: 99%

“…Seismically-defined faults either reactivate or cut across preexisting structures (Bezerra et al 2011). For example, Ferreira et al (2008) and Lopes et al (2010) concluded that the seismicity in the Caruaru and Belo Jardim areas reactivated the Pernambuco lineament, a continental-scale ductile shear zone ( Fig. 1), established at the end of the Neoproterozoic Brasiliano orogeny (Brito Neves et al 2000).…”

Section: Introductionmentioning

confidence: 99%

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Seismogenic faulting in the Meruoca granite, NE Brazil, consistent with a local weak fracture zone

Moura

Oliveira

Ferreira

et al. 2014

An. Acad. Bras. Ciênc.

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A sequence of earthquakes occurred in 2008 in the Meruoca granitic pluton, located in the northwestern part of the Borborema Province, NE Brazil. A seismological study defined the seismic activity occurring along the seismically-defined Riacho Fundo fault, a 081° striking, 8 km deep structure. The objective of this study was to analyze the correlation between this seismic activity and geological structures in the Meruoca granite. We carried out geological mapping in the epicentral area, analyzed the mineralogy of fault rocks, and compared the seismically-defined Riacho Fundo fault with geological data. We concluded that the seismically-defined fault coincides with ~E-W-striking faults observed at outcrop scale and a swarm of Mesozoic basalt dikes. We propose that seismicity reactivated brittle structures in the Meruoca granite. Our study highlights the importance of geological mapping and mineralogical analysis in order to establish the relationships between geological structures and seismicity at a given area.

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Section: Discussionmentioning

confidence: 80%

Section: Tectonic Features Of the Borborema Provincementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Seismogenic faulting in the Meruoca granite, NE Brazil, consistent with a local weak fracture zone

Moura

Oliveira

Ferreira

et al. 2014

An. Acad. Bras. Ciênc.

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“…LIMA NETO et al (2013) determined that this event and its aftershocks occurred along a fault *4 km long with a depth ranging between 2 and 8 km, all of them on the same fault plane that have a dip of 60°south. Lopes et al (2010) proposed that this ramification represents a ''weak zone'', which, combined with the present-day stress field (N-S tension), led to the reactivation of this fault segment (SYKES 1978;FERREIRA et al 2008). However, other geological structures under the same conditions have not shown any seismicity, which means that other local factors must be taken into account to explain the observed seismicity cases (LOPES et al 2010).…”

Section: Studied Area and Data Configurationmentioning

confidence: 99%

Detection of Subtle Hydromechanical Medium Changes Caused By a Small-Magnitude Earthquake Swarm in NE Brazil

D’Hour

Schimmel

Nascimento

et al. 2015

Pure Appl. Geophys.

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Abstract-Ambient noise correlation analyses are largely used in seismology to map heterogeneities and to monitor the temporal evolution of seismic velocity changes associated mostly with stress field variations and/or fluid movements. Here we analyse a small earthquake swarm related to a main m R 3.7 intraplate earthquake in North-East of Brazil to study the corresponding post-seismic effects on the medium. So far, post-seismic effects have been observed mainly for large magnitude events. In our study, we show that we were able to detect localized structural changes even for a small earthquake swarm in an intraplate setting. Different correlation strategies are presented and their performances are also shown. We compare the classical auto-correlation with and without pre-processing, including 1-bit normalization and spectral whitening, and the phase auto-correlation. The worst results were obtained for the pre-processed data due to the loss of waveform details. The best results were achieved with the phase cross-correlation which is amplitude unbiased and sensitive to small amplitude changes as long as there exist waveform coherence superior to other unrelated signals and noise. The analysis of 6 months of data using phase auto-correlation and cross-correlation resulted in the observation of a progressive medium change after the major recorded event. The progressive medium change is likely related to the swarm activity through opening new path ways for pore fluid diffusion. We further observed for the auto-correlations a lag time frequency-dependent change which likely indicates that the medium change is localized in depth. As expected, the main change is observed along the fault.

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“…Trabalhos de compilação dos casos de SDR no Brasil (Assumpção et al 2002;França et al 2009) geralmente não se aprofundam nesta discussão. Ferreira et al (2008a) discutiram o papel de estruturas dúcteis na geração dos sismos associados ao lineamento Pernambuco; enquanto Ferreira et al (2008b) atribuem a causa do evento de SDR da UHE Castanhão a um conjunto de falhas rúpteis que cortam a estrutura.…”

Section: Introductionunclassified

Influência de estruturas brasilianas na sismicidade desencadeada por reservatório na Usina Hidrelétrica de Irapé, Minas Gerais, Brasil

Silva¹,

Filho²,

Huelsen³

et al. 2014

Braz. J. Geol.

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RESUMO:Inaugurada em 2006, a Usina Hidrelétrica de Irapé possui a mais alta barragem do país, com 210 m, que vem sendo monitorada pelo Observatório Sismológico da Universidade de Brasília desde o começo do enchimento de seu reservatório. Apresentando sismicidade causada pelo aumento da tensão crustal logo após o início do represamento, a Sismicidade Desencadeada por Reservatório da Usina Hidrelétrica de Irapé permanece como um importante objeto de estudo para o entendimento deste fenômeno. O presente trabalho se propôs a estudar a sismicidade registrada de janeiro a maio de 2006, assim como a caracterizar a geologia ao redor da Usina Hidrelétrica de Irapé com o intuito de identificar e descrever as estruturas que permitam melhor compreender os eventos sísmicos. A orientação espacial dos eventos sísmicos obtidos pela análise das polaridades e da forma de onda condiz com aquelas dos lineamentos de relevo. As estruturas encontradas podem ser associadas a uma maior, de direção principal NE/SW, com dezenas de quilômetros, que seria responsável pela captura dos rios Jequitinhonha e Araçuaí, interpretada neste trabalho como uma estrutura relacionada a uma fase tardia do Evento Brasiliano. O diagrama de solução do mecanismo focal gerado utilizando um método de inversão da forma de onda no domínio do tempo indica que a direção dos possíveis planos de falhas está correlacionada ao principal direcionamento das estruturas rúpteis na área de trabalho. PALAVRAS-CHAVE: reativação sísmica de estruturas geológicas; estudos de sismicidade desencadeada por reservatório; Usina Hidrelétrica de Irapé.ABSTRACT: Inaugurated in 2006, the Irapé 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 Irapé 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 Araçuaí 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.

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The role of Precambrian mylonitic belts and present-day stress field in the coseismic reactivation of the Pernambuco lineament, Brazil

Cited by 86 publications

References 58 publications

Seismogenic faulting in the Meruoca granite, NE Brazil, consistent with a local weak fracture zone

Seismogenic faulting in the Meruoca granite, NE Brazil, consistent with a local weak fracture zone

Detection of Subtle Hydromechanical Medium Changes Caused By a Small-Magnitude Earthquake Swarm in NE Brazil

Influência de estruturas brasilianas na sismicidade desencadeada por reservatório na Usina Hidrelétrica de Irapé, Minas Gerais, Brasil

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