ISOLA a Fortran code and a Matlab GUI to perform multiple-point source inversion of seismic data

Sokos, Efthimios; Zahradnı́k, Jiřı́

doi:10.1016/j.cageo.2007.07.005

Cited by 347 publications

(158 citation statements)

References 8 publications

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“…Mesmo com porções específicas de um sismograma, é possível obter informações consideráveis sobre o evento sís-mico (Sokos & Zahradník 2008). No entanto, um estudo que considere na sua modelagem todo o sinal atribuído consegue melhores respostas para as perguntas em questão, levando-se em conta fatores de complexidade indubitada, como a heterogeneidade da crosta terrestre e a relação sinal e ruído, dentre outros.…”

Section: Materiais E Métodosunclassified

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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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Section: Materiais E Métodosunclassified

“…A rotina utilizada neste trabalho consiste na inversão ponto-a-ponto da forma de onda no domínio do tempo, trabalhada em linguagem FORTRAN e expressão gráfica do Matlab, denominada ISOLA e desenvolvida por Sokos & Zahradník (2008).…”

Section: Materiais E Métodosunclassified

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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“…To estimate the source parameters of the events, ISOLA software (Sokos and Zahradnik, 2008) was used. This program employs waveform modeling (inversion) to determine the focal mechanism and the scalar seismic moment.…”

Section: Source Parametersmentioning

confidence: 99%

“…ISOLA software is based on a multiple point-source representation and an iterative deconvolution method, similar to Kikuchi and Kanamori (1991) for teleseismic records, but here the full wave field is considered and Green's functions are calculated by the discrete wavenumber method of Bouchon (1981). Thus, the method is applicable for regional and local events (Sokos and Zahradnik, 2008). The code transforms velocity into displacement, inverts the displacement, and provides synthetic displacement (Sokos and Zahradnik, 2008).…”

Section: Source Parametersmentioning

confidence: 99%

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Seismicity at the northeast edge of the Mexican Volcanic Belt (MVB) and activation of an undocumented fault: the Peñamiller earthquake sequence of 2010–2011, Querétaro, Mexico

Clemente-Chavez

Figueroa-Soto²,

Zúñiga³

et al. 2013

Nat. Hazards Earth Syst. Sci.

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Abstract. The town of Peñamiller in the state of Querétaro, Mexico, is located at the northeast border of the seismogenic zone known as the Mexican Volcanic Belt (MVB), which transects the central part of Mexico with an east–west orientation. In the vicinity of this town, a sequence of small earthquakes occurred during the end of 2010 and beginning of 2011. Seismicity in the continental regimen of central Mexico is not too frequent; however, it is known that there are precedents of large earthquakes (Mw magnitude greater than 6.0) occurring in this zone. Three large earthquakes have occurred in the past 100 yr: the 19 November 1912 (MS = 7.0), the 3 January 1920 (MS = 6.4), and the 29 June 1935 (MS = 6.9) earthquakes. Prior to the instrumental period, the earthquake of 11 February 1875, which took place near the city of Guadalajara, caused widespread damage. The purpose of this article is to contribute to the available seismic information of this region. This will help advance our understanding of the tectonic situation of the central Mexico MVB region. Twenty-four shallow earthquakes of the Peñamiller seismic sequence of 2011 were recorded by a temporary accelerograph network installed by the Universidad Autónoma de Querétaro (UAQ). The data were analyzed in order to determine the source locations and to estimate the source parameters. The study was carried out through an inversion process and by spectral analysis. The results show that the largest earthquake occurred on 8 February 2011 at 19:53:48.6 UTC, had a moment magnitude Mw = 3.5, and was located at latitude 21.039° and longitude −99.752°, at a depth of 5.6 km. This location is less than 7 km away in a south-east direction from downtown Peñamiller. The focal mechanisms are mostly normal faults with small lateral components. These focal mechanisms are consistent with the extensional regimen of the southern extension of the Basin and Range (BR) province. The source area of the largest event was estimated to have a radius of 0.5 km, which corresponds to a normal fault with azimuth of 174° and an almost pure dip slip. Peak ground acceleration (PGA) was close to 100 cm s−2 in the horizontal direction. Shallow earthquakes induced by crustal faulting present a potential seismic risk and hazard within the MVB, considering the population growth. Thus, the necessity to enrich seismic information in this zone is very important since the risk at most urban sites in the region might even be greater than that posed by subduction earthquakes.

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Nonisotropic radiation of the 2013 North Korean nuclear explosion

Vavryčuk

Kim²

2014

Geophysical Research Letters

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On 12 February 2013, North Korea conducted an underground nuclear test in the northeastern mountainous part of the country. The explosion reached magnitude m b = 5.1 being recorded at most of seismic stations around the world and becoming one of the best ever recorded nuclear explosions in history. Similarly, as other nuclear explosions buried in Nevada, Kazakhstan, or China, the 2013 North Korean explosion is characterized by a significant nonisotropic radiation. This radiation is manifested by distinct SH and Love waves in the wave field and is inconsistent with the model of a spherically symmetric source. We show that the Love waves are not generated by a tectonic earthquake triggered on a nearby fault structures but produced by asymmetry of the explosive source caused by presence of deviatoric stress in the surrounding rock. The retrieved moment tensor of the 2013 explosion is characterized by the isotropic component of 57 ± 5%, the double-couple component of 17 ± 9%, and the compensated linear vector dipole component of 24 ± 7%. The P, T, and N axes of the moment tensor are consistent with the principal axes of the regional tectonic stress in the Korean Peninsula. A comparison of waveforms and particle motions of the 2013 explosion and the previous North Korean nuclear explosion buried in 2009 indicates that the 2013 explosion was slightly more nonisotropic.

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ISOLA a Fortran code and a Matlab GUI to perform multiple-point source inversion of seismic data

Cited by 347 publications

References 8 publications

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

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

Seismicity at the northeast edge of the Mexican Volcanic Belt (MVB) and activation of an undocumented fault: the Peñamiller earthquake sequence of 2010–2011, Querétaro, Mexico

Nonisotropic radiation of the 2013 North Korean nuclear explosion

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