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Title

Crustal seismic structure beneath Portugal and southern Galicia (Western Iberia) and the role of Variscan inheritance

AuthorsVeludo, I.; Dias, Nuno A.; Fonseca, P. E.; Matias, L.; Carrilho, F.; Haberland, C.; Villaseñor, Antonio
KeywordsCrustal structure
Earthquakes
Portugal
Seismic tomography
Variscan orogeny
Issue DateNov-2017
PublisherElsevier
CitationTectonophysics, 717: 645-664 (2017)
AbstractThe crustal structure in Western Iberia, is the result of a complex geodynamic history. Most of the surface is covered by rocks dating to the Variscan orogeny, the coastal ranges dominated by Mesozoic structures and Mesocenozoic basins covering partially the mainland. In this study we present the results of a local earthquake tomographic study, performed to image in depth this complex crustal structure down to 24 km depth. The obtained tomograms present a good correlation with the surface geology, in general with higher Vp velocities in the north, and lower Vp velocities in the south. The heterogeneity observed on the surface geology of the Galicia-Tras-os-Montes Zone is well marked, being a relatively thin layer over the smoother structure of the Centro Iberia Zone CIZ. The CIZ crustal block confined between the Porto-Tomar-Ferreira do Alentejo and the Manteigas-Bragança faults having higher Vp values, enhancing the contrast to the Lusitanian Basin to the west. The Ossa-Morena Zone corresponds to the unit presenting the greater heterogeneity in both Vp and Vp/Vs models, showing also with a complex transition to the South Portuguese Zone and a relatively smooth transition to the Centro Iberian Zone. Unexpectedly, the South Portuguese Zone present an east-west velocity variation with no apparent correspondence with the surface geology. The transition to the coastal Mesocenozoic basins is clearly marked, the Lower Tagus Valley corresponding to a ~ 4 km thick low velocity region. The relocation inland recorded seismicity in the period 2000–2014 allows cleansing some of the alignments and establish their correlation with some of the active structures in Portugal. The model features and seismicity pattern reveal the strong role played by the Variscan heritage. © 2017 Elsevier B.V.
Publisher version (URL)https://doi.org/10.1016/j.tecto.2017.08.018
URIhttp://hdl.handle.net/10261/157054
DOI10.1016/j.tecto.2017.08.018
ISSN0040-1951
E-ISSN1879-3266
Appears in Collections:(ICTJA) Artículos
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