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Tsunamigenic-seismogenic structures, neotectonics, sedimentary processes and slope instability on the southwest Portuguese Margin

Tsunamigenic-seismogenic structures, neotectonics, sedimentary processes and slope instability on the southwest Portuguese Margin
Tsunamigenic-seismogenic structures, neotectonics, sedimentary processes and slope instability on the southwest Portuguese Margin
Tectonically active structures prone to cause devastating earthquakes and tsunamis, e.g. the Lisbon 1755 earthquake, were investigated during the UNESCO/IOC Training Through Research-10 (TTR-10) cruise on the southwest Portuguese Continental Margin using single channel seismic profiles, a 3.5-kHz hull-mounted sea-bottom profiler, 10-kHz OKEAN long range side-scan sonar, 30-kHz ORETECH deep-towed side-scan sonar, and a high-resolution deep-towed sea-bottom profiler. These data allowed the definition of new active faults and the establishment of morphological criteria for the classification of active faults in the study area. Landslides associated with the activity of a major tectonic structure, the Marquês de Pombal Fault, and other areas with clear signs of mass wasting phenomena were mapped. A slope-to-basin sedimentary system comprising 21 sedimentary ridges up to 20 km long was mapped and described. It was found that the sediments are mainly transported into the deep basins by mass transport processes across the steepest fault scarps forming a channel–levee system, while gravitational slides/slumps dominate the shallower slopes. The sedimentary ridges with an elevation of 40–50 m (50–60 ms TWT) above the seafloor are imaged on the high-resolution seismic profiles as an alternation of high and low amplitude reflectors. It is shown that the Pereira de Sousa Fault, its plateau and the Príncipes de Avis Plateau are experiencing uplift according to sedimentary and morphological criteria.
neotectonics, earthquake, tsunami, active fault scarps, sedimentary ridges, gravitational slides, passive–active margin transition
0025-3227
235-258
Terrinha, P.
e7a8cad1-3f89-4257-88d0-8d661cf476a5
Pinheiro, L. M.
93fcbbb5-d878-4231-ae38-a14eea62a0f4
Henriet, J.-P.
c2065e32-e628-4f6d-9a8e-ce67a06fa444
Matias, L.
a5fbf1ef-3a81-47cd-a672-2ec70205e7f8
Ivanov, M. K.
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Monteiro, J. H.
615d1217-ae94-4b4b-82e1-1cc314f15e1a
Akhmetzhanov, A.
c46da8d8-8b9f-404b-9b57-9f669d37d781
Volkonskaya, A.
1dd870ab-a86a-4dc3-afcc-b3a7a55bd259
Cunha, T.
c70c5d09-fa32-4799-907f-e6dc284e5432
Shaskin, P.
978534bc-2eb7-4123-a5b2-21d8c239a23c
Rovere, M.
5844f096-2f36-4195-9ebf-6d4820b32a41
Terrinha, P.
e7a8cad1-3f89-4257-88d0-8d661cf476a5
Pinheiro, L. M.
93fcbbb5-d878-4231-ae38-a14eea62a0f4
Henriet, J.-P.
c2065e32-e628-4f6d-9a8e-ce67a06fa444
Matias, L.
a5fbf1ef-3a81-47cd-a672-2ec70205e7f8
Ivanov, M. K.
9e69dfe8-e644-49e1-93ae-295671ea3b8d
Monteiro, J. H.
615d1217-ae94-4b4b-82e1-1cc314f15e1a
Akhmetzhanov, A.
c46da8d8-8b9f-404b-9b57-9f669d37d781
Volkonskaya, A.
1dd870ab-a86a-4dc3-afcc-b3a7a55bd259
Cunha, T.
c70c5d09-fa32-4799-907f-e6dc284e5432
Shaskin, P.
978534bc-2eb7-4123-a5b2-21d8c239a23c
Rovere, M.
5844f096-2f36-4195-9ebf-6d4820b32a41

Terrinha, P., Pinheiro, L. M., Henriet, J.-P., Matias, L., Ivanov, M. K., Monteiro, J. H., Akhmetzhanov, A., Volkonskaya, A., Cunha, T., Shaskin, P. and Rovere, M. (2002) Tsunamigenic-seismogenic structures, neotectonics, sedimentary processes and slope instability on the southwest Portuguese Margin. Marine Geology, 195 (1-4), 235-258. (doi:10.1016/S0025-3227(02)00682-5).

Record type: Article

Abstract

Tectonically active structures prone to cause devastating earthquakes and tsunamis, e.g. the Lisbon 1755 earthquake, were investigated during the UNESCO/IOC Training Through Research-10 (TTR-10) cruise on the southwest Portuguese Continental Margin using single channel seismic profiles, a 3.5-kHz hull-mounted sea-bottom profiler, 10-kHz OKEAN long range side-scan sonar, 30-kHz ORETECH deep-towed side-scan sonar, and a high-resolution deep-towed sea-bottom profiler. These data allowed the definition of new active faults and the establishment of morphological criteria for the classification of active faults in the study area. Landslides associated with the activity of a major tectonic structure, the Marquês de Pombal Fault, and other areas with clear signs of mass wasting phenomena were mapped. A slope-to-basin sedimentary system comprising 21 sedimentary ridges up to 20 km long was mapped and described. It was found that the sediments are mainly transported into the deep basins by mass transport processes across the steepest fault scarps forming a channel–levee system, while gravitational slides/slumps dominate the shallower slopes. The sedimentary ridges with an elevation of 40–50 m (50–60 ms TWT) above the seafloor are imaged on the high-resolution seismic profiles as an alternation of high and low amplitude reflectors. It is shown that the Pereira de Sousa Fault, its plateau and the Príncipes de Avis Plateau are experiencing uplift according to sedimentary and morphological criteria.

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More information

Published date: 2002
Keywords: neotectonics, earthquake, tsunami, active fault scarps, sedimentary ridges, gravitational slides, passive–active margin transition

Identifiers

Local EPrints ID: 63096
URI: http://eprints.soton.ac.uk/id/eprint/63096
ISSN: 0025-3227
PURE UUID: c1ea298c-869c-4fce-9110-bc3aa44a7b5d

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Date deposited: 09 Sep 2008
Last modified: 15 Mar 2024 11:34

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Contributors

Author: P. Terrinha
Author: L. M. Pinheiro
Author: J.-P. Henriet
Author: L. Matias
Author: M. K. Ivanov
Author: J. H. Monteiro
Author: A. Akhmetzhanov
Author: A. Volkonskaya
Author: T. Cunha
Author: P. Shaskin
Author: M. Rovere

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