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Macrossismicidade associada ao sismo de Arraiolos do dia 15 de janeiro de 2018 com M = 4,9 e eventuais implicações na geometria da rutura

2020-08Journal article Open access
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dc.contributor.authorAraujo, A.
dc.contributor.authorCaldeira, Bento
dc.contributor.authorMartins, Antonio
dc.contributor.authorBorges, José Fernando
dc.contributor.authorMoreira, Noel
dc.contributor.authorFonseca Araújo, Joana
dc.contributor.authorMaia, Miguel
dc.contributor.authorVicente, S.
dc.contributor.authorAfonso, P.
dc.contributor.authorEspanhol, D.
dc.contributor.authorBezzeghoud, Mourad
dc.date.accessioned2022-02-23T18:16:35Z
dc.date.available2022-02-23T18:16:35Z
dc.date.issued2020-08
dc.description.abstractRESUMO: Na segunda quinzena de janeiro de 2018 realizou-se um estudo da macrossismicidade associada ao sismo de Arraiolos de dia 15 de janeiro. No presente trabalho descreve-se a metodologia usada na recolha de informação, o tratamento dos dados e a sua representação na forma de mapa de intensidades. A distribuição geográfica das intensidades mostra um alongamento da isossista de intensidade IV na direção N-S e no sentido sul. Este alongamento poderá estar relacionado com uma variação lateral da atenuação, ou com um efeito de sítio. Outra hipótese, menos provável, é que este padrão se deva ao efeito de diretividade originado por uma rutura unilateral com propagação de norte para sul, ao longo de um plano do mecanismo focal. Esta possibilidade, conjugada com evidências para a existência de estruturas ativas WNW-ESE descritas em trabalhos anteriores, levanta a hipótese do designado “cluster sísmico de Arraiolos” estar associado a uma interseção de falhas ativas.pt_PT
dc.description.abstractABSTRACT: We performed a study about the macrossismicity associated to the Arraiolos (Portugal) earthquake, that occurred on January 15th, (M = 4.9), in order to construct a map of seismic intensities. The fieldwork took place in the second half of January, using the questionnaire available in the website of the Portuguese Institute of the Sea and the Atmosphere (IPMA). We provided the same questionnaire on the internet, and collected responses from many parts of the country. The results obtained allowed to construct a map of intensities showing a clear elongation of the intensities in a N-S direction. This orientation can be explained by the differences in the behaviour of seismic waves depending on the nature of the rocks or by a directivity effect associated with the rupture along a fault with this direction. On the one hand, an earthquake of magnitude 4.9 will hardly have the capacity to produce a directivity effect, however on the other hand the analysis of the Portuguese Geological Map seems to discard the first hypothesis. The IPMA provides on its website, a strike slip focal mechanism for this earthquake (E-W dextral and N-S sinistral). The conjugation of this focal mechanism with the distribution of intensities, seems to reinforce the hypothesis of rupture along an N-S fault plane. Similar focal mechanisms are known, associated with other earthquakes that occurred in this region, but previous works propose that they are related, not toN-Sruptures, buttoWNW-ESE structures present in the region, with geological and geomorphological evidence of recent tectonic activity. In this type of studies, there is always a factor ofsubjectivity inherent to the sensitivity of the people who were questioned, so these data are not sufficient to clearly affirm that the earthquake occurred associated with a N-S-trending fault. The combination of these data with the information published in previous works allows to consider the possibility that the "Arraiolos seismic cluster" corresponds to an intersection of active WNW-ESE and N-S strike slip faults. Assuming that there are alternating ruptures in both systems, temporary block occurs in the system that has been cut, leading to a local stress concentration. Though, a movement that in depth can be ductile, aseismic throughout most of the area of the faults, in the zone of intersection of the two systems the crust will have to respond necessarily as brittle, generating earthquakes and explaining the existence of this seismic cluster.pt_PT
dc.description.versioninfo:eu-repo/semantics/publishedVersionpt_PT
dc.identifier.citationAraújo et al. 2020, ‘Macrossismicidade associada ao sismo de Arraiolos do dia 15 de janeiro de 2018 com M = 4,9 e eventuais implicações na geometria da rutura’, Comunicações Geológicas, vol. 107, nº 1 (especial), pp. 35-37.pt_PT
dc.identifier.doihttps://doi.org/10.34637/kn9m-er29
dc.identifier.eissn1647-581X
dc.identifier.issn0873-948X
dc.identifier.urihttp://hdl.handle.net/10400.9/3767
dc.language.isoporpt_PT
dc.peerreviewedyespt_PT
dc.publisherLNEG - Laboratório Nacional de Energia e Geologiapt_PT
dc.relationFundação para a Ciência e Tecnologia através do programa plurianual do Instituto de Ciências da Terra, UID/GEO/04683.pt_PT
dc.relation.publisherversionhttps://www.lneg.pt/wp-content/uploads/2020/09/07_Araujo-etal.pdfpt_PT
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/pt_PT
dc.subjectSismopt_PT
dc.subjectIntensidade sísmicapt_PT
dc.subjectArraiolospt_PT
dc.subjectEarthquakept_PT
dc.subjectSeismic intensitypt_PT
dc.titleMacrossismicidade associada ao sismo de Arraiolos do dia 15 de janeiro de 2018 com M = 4,9 e eventuais implicações na geometria da ruturapt_PT
dc.title.alternativeMacrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupturept_PT
dc.typejournal article
dspace.entity.typePublication
oaire.citation.conferencePlaceAmadorapt_PT
oaire.citation.endPage37pt_PT
oaire.citation.issueFascículo especial Ipt_PT
oaire.citation.startPage35pt_PT
oaire.citation.titleComunicações Geológicaspt_PT
oaire.citation.volume107pt_PT
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rcaap.rightsopenAccesspt_PT
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Volume 107 (2020) Fascículo Especial I (X Congresso Nacional de Geologia)