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

Morphostructure, tectono-sedimentary evolution and seismic potential of the Horseshoe Fault, SW Iberian Margin
Morphostructure, tectono-sedimentary evolution and seismic potential of the Horseshoe Fault, SW Iberian Margin
High-resolution acoustic and seismic data acquired 100 km offshore Cape São 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 (Mw > 6) occurred in the SW Iberian Margin. The HF corresponds to a N40 trending, 110 km long, and NW-verging active thrust that affects the whole sedimentary sequence and reaches up to the seafloor, generating a relief of more than 1 km. 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°) 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 Mw 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.
0950-091X
382–400
Martínez-Loriente, Sara
0758e680-e76f-4145-a200-7d52af9fddf0
Gràcia, Eulàlia
4cdbab2b-dd60-496b-aeef-76ae9c30e48d
Bartolome, Rafael
8ca8d659-da03-4162-91fe-4c4307010931
Perea, Hector
9f6271fb-8397-49aa-8950-5b1032e721b7
Klaeschen, Dirk
6f4c994a-036e-44cc-b35e-c85e894f1bac
Dañobeitia, Juan José
d7e4f186-82a1-4461-8440-752b66b41ed5
Zitellini, Nevio
cd03c216-6a4c-43cb-8389-28510ec68f17
Wynn, Russell B.
72ccd765-9240-45f8-9951-4552b497475a
Masson, Douglas G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45
Martínez-Loriente, Sara
0758e680-e76f-4145-a200-7d52af9fddf0
Gràcia, Eulàlia
4cdbab2b-dd60-496b-aeef-76ae9c30e48d
Bartolome, Rafael
8ca8d659-da03-4162-91fe-4c4307010931
Perea, Hector
9f6271fb-8397-49aa-8950-5b1032e721b7
Klaeschen, Dirk
6f4c994a-036e-44cc-b35e-c85e894f1bac
Dañobeitia, Juan José
d7e4f186-82a1-4461-8440-752b66b41ed5
Zitellini, Nevio
cd03c216-6a4c-43cb-8389-28510ec68f17
Wynn, Russell B.
72ccd765-9240-45f8-9951-4552b497475a
Masson, Douglas G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45

Martínez-Loriente, Sara, Gràcia, Eulàlia, Bartolome, Rafael, Perea, Hector, Klaeschen, Dirk, Dañobeitia, Juan José, Zitellini, Nevio, Wynn, Russell B. and Masson, Douglas G. (2018) Morphostructure, tectono-sedimentary evolution and seismic potential of the Horseshoe Fault, SW Iberian Margin. Basin Research, 30 (Suppl 1), 382–400. (doi:10.1111/bre.12225).

Record type: Article

Abstract

High-resolution acoustic and seismic data acquired 100 km offshore Cape São 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 (Mw > 6) occurred in the SW Iberian Margin. The HF corresponds to a N40 trending, 110 km long, and NW-verging active thrust that affects the whole sedimentary sequence and reaches up to the seafloor, generating a relief of more than 1 km. 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°) 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 Mw 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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More information

Accepted/In Press date: 23 October 2016
e-pub ahead of print date: 9 December 2016
Published date: 1 February 2018
Organisations: Marine Geoscience

Identifiers

Local EPrints ID: 403833
URI: https://eprints.soton.ac.uk/id/eprint/403833
ISSN: 0950-091X
PURE UUID: d233f89a-c792-4b61-ba64-df5bbd275199

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Date deposited: 12 Dec 2016 17:14
Last modified: 16 Jan 2018 17:31

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Contributors

Author: Sara Martínez-Loriente
Author: Eulàlia Gràcia
Author: Rafael Bartolome
Author: Hector Perea
Author: Dirk Klaeschen
Author: Juan José Dañobeitia
Author: Nevio Zitellini
Author: Russell B. Wynn
Author: Douglas G. Masson

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