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Earthquakes in western Iberia: improving the understanding of lithospheric deformation in a slowly deforming region

2015-10Journal article Restricted access
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dc.contributor.authorCustódio, Susana
dc.contributor.authorDias, Nuno
dc.contributor.authorCarrilho, F.
dc.contributor.authorGóngora, E.
dc.contributor.authorRio, I.
dc.contributor.authorMarreiros, Célia
dc.contributor.authorMorais, Iolanda
dc.contributor.authorAlves, P.
dc.contributor.authorMatias, Luís
dc.date.accessioned2016-04-28T10:19:43Z
dc.date.available2016-04-28T10:19:43Z
dc.date.issued2015-10
dc.description.abstractMainland Portugal, on the southwestern edge of the European continent, is located directly north of the boundary between the Eurasian and Nubian plates. It lies in a region of slow lithospheric deformation (< 5 mm yr(-1)), which has generated some of the largest earthquakes in Europe, both intraplate (mainland) and interplate (offshore). Some offshore earthquakes are nucleated on old and cold lithospheric mantle, at depths down to 60 km. The seismicity of mainland Portugal and its adjacent offshore has been repeatedly classified as diffuse. In this paper, we analyse the instrumental earthquake catalogue for western Iberia, which covers the period between 1961 and 2013. Between 2010 and 2012, the catalogue was enriched with data from dense broad-band deployments. We show that although the plate boundary south of Portugal is diffuse, in that deformation is accommodated along several distributed faults rather than along one long linear plate boundary, the seismicity itself is not diffuse. Rather, when located using high-quality data, earthquakes collapse into well-defined clusters and lineations. We identify and characterize the most outstanding clusters and lineations of epicentres and correlate them with geophysical and tectonic features (historical seismicity, topography, geologically mapped faults, Moho depth, free-air gravity, magnetic anomalies and geotectonic units). Both onshore and offshore, clusters and lineations of earthquakes are aligned preferentially NNE-SSW and WNW-ESE. Cumulative seismic moment and epicentre density decrease from south to north, with increasing distance from the plate boundary. Only few earthquake lineations coincide with geologically mapped faults. Clusters and lineations that do not match geologically mapped faults may correspond to previously unmapped faults (e.g. blind faults), rheological boundaries or distributed fracturing inside blocks that are more brittle and therefore break more easily than neighbour blocks. The seismicity map of western Iberia presented in this article opens important questions concerning the regional seismotectonics. This work shows that the study of low-magnitude earthquakes using dense seismic deployments is a powerful tool to study lithospheric deformation in slowly deforming regions, such as western Iberia, where high-magnitude earthquakes occur with long recurrence intervals.pt_PT
dc.identifier.citationCUSTÓDIO, Susana; [et al] - Earthquakes in western Iberia: improving the understanding of lithospheric deformation in a slowly deforming region. Geophysical Journal International. ISSN 0956-540X. Vol. 203, N.º 1 (2015), pp. 127-145pt_PT
dc.identifier.doi10.1093/gji/ggv285pt_PT
dc.identifier.issn0956-540X
dc.identifier.issn1365-246X
dc.identifier.urihttp://hdl.handle.net/10400.21/6110
dc.language.isoengpt_PT
dc.peerreviewedyespt_PT
dc.publisherOxford University Presspt_PT
dc.subjectEarthquake source observationspt_PT
dc.subjectSeismicity and tectonicspt_PT
dc.subjectIntra-plate processespt_PT
dc.subjectDynamicspt_PT
dc.subjectSeismotectonicspt_PT
dc.subjectNeotectonicspt_PT
dc.titleEarthquakes in western Iberia: improving the understanding of lithospheric deformation in a slowly deforming regionpt_PT
dc.typejournal article
dspace.entity.typePublication
oaire.citation.endPage145pt_PT
oaire.citation.issue1pt_PT
oaire.citation.startPage127pt_PT
oaire.citation.titleGeophysical Journal Internationalpt_PT
oaire.citation.volume203pt_PT
person.familyNameDias
person.givenNameNuno
person.identifier1348964
person.identifier.ciencia-idDB10-5086-2205
person.identifier.orcid0000-0001-7672-4476
person.identifier.ridB-2778-2008
person.identifier.scopus-author-id56640885300
rcaap.rightsclosedAccesspt_PT
rcaap.typearticlept_PT
relation.isAuthorOfPublicationd7e4c7da-29b6-439f-ab4a-f5d94c1d7ca5
relation.isAuthorOfPublication.latestForDiscoveryd7e4c7da-29b6-439f-ab4a-f5d94c1d7ca5

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