Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupture
Autor(a) principal: | |
---|---|
Data de Publicação: | 2020 |
Outros Autores: | , , , , , , , , , |
Tipo de documento: | Artigo |
Idioma: | por |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/10174/28279 |
Resumo: | 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 intensi- ties 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 to N-S ruptures, but to WNW-ESE structures present in the region, with geolog- ical and geomorphological evidence of recent tectonic activity. In this type of studies, there is always a factor of subjectivity 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 com- bination 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. |
id |
RCAP_8b72d7905c21ba767f54bbb556fefab3 |
---|---|
oai_identifier_str |
oai:dspace.uevora.pt:10174/28279 |
network_acronym_str |
RCAP |
network_name_str |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
repository_id_str |
7160 |
spelling |
Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the ruptureEarthquakesseismic intensityArraiolosWe 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 intensi- ties 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 to N-S ruptures, but to WNW-ESE structures present in the region, with geolog- ical and geomorphological evidence of recent tectonic activity. In this type of studies, there is always a factor of subjectivity 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 com- bination 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.Os autores agradecem à Fundação para a Ciência e Tecnologia o fi- nanciamento recebido através do programa plurianual do Instituto de Ciências da Terra, UID/GEO/0468LNEG2020-11-03T12:03:10Z2020-11-032020-08-01T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articlehttp://hdl.handle.net/10174/28279http://hdl.handle.net/10174/28279porAraújo A., B. Caldeira, A. Martins, J. Borges, N. Moreira, J. Araújo, M. Maia, S. Vicente, P. Afonso, D. Espanhol, M. Bezzeghoud, 2020. Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupture. Comunicações Geológicas (2020) 107, Especial I, 35-3. ISSN: 0873-948X; e-ISSN: 1647-581X. https://www.lneg.pt/wp-content/uploads/2020/05/Volume_107.pdf0873-948Xhttps://www.lneg.pt/wp-content/uploads/2020/05/Volume_107.pdfComunicações GeológicasFIS, GEOaaraujo@uevora.ptbafcc@uevora.ptaam@uevora.ptjborges@uevora.ptnafm@uevora.ptndndndndndmourad@uevora.pt393Araújo, AlexandreCaldeira, BentoMartins, AntónioBorges, J. FernandoMoreira, NoelAraújo, JoanaMaia, MiguelVicente, S.Afonso, P.Espanhol, D.Bezzeghoud, Mouradinfo:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2024-01-03T19:24:32Zoai:dspace.uevora.pt:10174/28279Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-20T01:18:13.022974Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupture |
title |
Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupture |
spellingShingle |
Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupture Araújo, Alexandre Earthquakes seismic intensity Arraiolos |
title_short |
Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupture |
title_full |
Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupture |
title_fullStr |
Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupture |
title_full_unstemmed |
Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupture |
title_sort |
Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupture |
author |
Araújo, Alexandre |
author_facet |
Araújo, Alexandre Caldeira, Bento Martins, António Borges, J. Fernando Moreira, Noel Araújo, Joana Maia, Miguel Vicente, S. Afonso, P. Espanhol, D. Bezzeghoud, Mourad |
author_role |
author |
author2 |
Caldeira, Bento Martins, António Borges, J. Fernando Moreira, Noel Araújo, Joana Maia, Miguel Vicente, S. Afonso, P. Espanhol, D. Bezzeghoud, Mourad |
author2_role |
author author author author author author author author author author |
dc.contributor.author.fl_str_mv |
Araújo, Alexandre Caldeira, Bento Martins, António Borges, J. Fernando Moreira, Noel Araújo, Joana Maia, Miguel Vicente, S. Afonso, P. Espanhol, D. Bezzeghoud, Mourad |
dc.subject.por.fl_str_mv |
Earthquakes seismic intensity Arraiolos |
topic |
Earthquakes seismic intensity Arraiolos |
description |
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 intensi- ties 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 to N-S ruptures, but to WNW-ESE structures present in the region, with geolog- ical and geomorphological evidence of recent tectonic activity. In this type of studies, there is always a factor of subjectivity 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 com- bination 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. |
publishDate |
2020 |
dc.date.none.fl_str_mv |
2020-11-03T12:03:10Z 2020-11-03 2020-08-01T00:00:00Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10174/28279 http://hdl.handle.net/10174/28279 |
url |
http://hdl.handle.net/10174/28279 |
dc.language.iso.fl_str_mv |
por |
language |
por |
dc.relation.none.fl_str_mv |
Araújo A., B. Caldeira, A. Martins, J. Borges, N. Moreira, J. Araújo, M. Maia, S. Vicente, P. Afonso, D. Espanhol, M. Bezzeghoud, 2020. Macrossismicity associated with the Arraiolos earthquake of January 15, 2018 with M = 4.9 and possible implications in the geometry of the rupture. Comunicações Geológicas (2020) 107, Especial I, 35-3. ISSN: 0873-948X; e-ISSN: 1647-581X. https://www.lneg.pt/wp-content/uploads/2020/05/Volume_107.pdf 0873-948X https://www.lneg.pt/wp-content/uploads/2020/05/Volume_107.pdf Comunicações Geológicas FIS, GEO aaraujo@uevora.pt bafcc@uevora.pt aam@uevora.pt jborges@uevora.pt nafm@uevora.pt nd nd nd nd nd mourad@uevora.pt 393 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.publisher.none.fl_str_mv |
LNEG |
publisher.none.fl_str_mv |
LNEG |
dc.source.none.fl_str_mv |
reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação instacron:RCAAP |
instname_str |
Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
instacron_str |
RCAAP |
institution |
RCAAP |
reponame_str |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
collection |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
repository.name.fl_str_mv |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
repository.mail.fl_str_mv |
|
_version_ |
1799136664233181184 |