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Morphostructure, tectono-sedimentary evolution and seismic potential of the Horseshoe Fault, SW Iberian Margin

TitleMorphostructure, tectono-sedimentary evolution and seismic potential of the Horseshoe Fault, SW Iberian Margin
Publication TypeJournal Article
Year of Publication2018
AuthorsMartinez-Loriente S., Gracia E., Bartolome R., Perea H., Klaeschen D., Danobeitia J.J, Zitellini N., Wynn R.B, Masson D.G
JournalBasin Research
Date Published2018/02
Type of ArticleArticle
ISBN Number0950-091X
Accession NumberWOS:000419873300020
Keywordsafrica; cascadia subduction zone; central atlantic; compressional; deformation; eurasia plate boundary; focal mechanisms; gibraltar; gorringe bank; north-atlantic; tectonic implications

High-resolution acoustic and seismic data acquired 100km offshore Cape SAo Vicente, image with unprecedented detail one of the largest active reverse faults of the SW Iberian Margin, the Horseshoe Fault (HF). The HF region is an area seismogenically active, source of the largest magnitude instrumental and historical earthquake (M-w>6) occurred in the SW Iberian Margin. The HF corresponds to a N40 trending, 110km long, and NW-verging active thrust that affects the whole sedimentary sequence and reaches up to the seafloor, generating a relief of more than 1km. The along-strike structural variability as well as fault trend suggests that the HF is composed by three main sub-segments: North (N25), Central (N50) and South (N45). Swath-bathymetry, TOBI sidescan sonar backscatter and parametric echosounder TOPAS profiles reveal the surface morphology of the HF block, characterized by several, steep (20 degrees) small scarps located on the hangingwall, and a succession of mass transport deposits (i.e. turbidites) on its footwall, located in the Horseshoe Abyssal Plain. A succession of pre-stack depth-migrated multichannel seismic reflection profiles across the HF and neighbouring areas allowed us to constrain their seismo-stratigraphy, structural geometry, tectono-sedimentary evolution from Upper Jurassic to present-day, and to calculate their fault parameters. Finally, on the basis of segment length, surface fault area and seismogenic depth we evaluated the seismic potential of the HF, which in the worst-case scenario may generate an earthquake of magnitude M-w 7.8 +/- 0.1. Thus, considering the tectonic behaviour and near-shore location, the HF should be recognized in seismic and tsunami hazard assessment models of Western Europe and North Africa.

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