Active faulting offshore SE Spain (Alboran Sea)

Implications for earthquake hazard assessment in the Southern Iberian Margin

Eulàlia Gràcia, Raimon Pallàs, Juan Ignacio Soto, Menchu Comas, Ximena Moreno, Eulàlia Masana, Pere Santanach, Susana Diez, Margarita García, Juanjo Dañobeitia, R. Bartolomé, M. Farrán, M. Gómez, M. J.R. Alpiste, G. Lastras, V. Wilmott, H. Perea, P. Blondel, O. Gómez, L. Bullock & 7 others C. Jacobs, I. Rouse, D. White, S. Whittle, P. Terrinha, J. Gafeira, C. Roque

Research output: Contribution to journalArticle

97 Citations (Scopus)

Abstract

The southern margin of the Iberian Peninsula hosts the convergent boundary between the European and African Plates. The area is characterised by low to moderate magnitude shallow earthquakes, although large historical events have also occurred. In order to determine the possible sources of these events, we recently acquired swath-bathymetry, TOBI sidescan sonar and high-resolution seismic data on the Almería Margin (Eastern Alboran Sea). The new dataset reveals the offshore continuation of the NE-SW trending Carboneras Fault, a master fault in the Eastern Betic Shear Zone, and its associated structures (N150 and NS faults). These structures are active since they cut the Late Quaternary sedimentary units. The submarine Carboneras Fault zone is 100 km long, 5-10 km wide, and is divided into two N045 and N060 segments separated by an underlapping restraining stepover. Geomorphic features typically found in subaerial strike-slip faults, such as deflected drainage, water gaps, shutter ridges, pressure ridges and "en echelon" folds suggest a strike-slip motion combined with a vertical component along the submarine Carboneras Fault. Considering the NNW-SSE regional shortening axis, a left-lateral movement is deduced for the Carboneras Fault, whereas right-lateral and normal components are suggested for the associated N150 and NS faults, respectively. The offshore portion of this fault is at least twice as long as its onshore portion and together they constitute one of the longest structures in the southeastern Iberian Margin. Despite the fact that present day seismicity in the Almería margin seems to be associated with the N150 to NS faults, the Carboneras Fault is a potential source of large magnitude (Mw ∼7.2) events. Hence, the Carboneras Fault zone could pose a significant earthquake and tsunami hazard to the coasts of Spain and North Africa, and should therefore be considered in any hazard re-evaluation.

Original languageEnglish
Pages (from-to)734-749
Number of pages16
JournalEarth and Planetary Science Letters
Volume241
Issue number3-4
Early online date27 Dec 2005
DOIs
Publication statusPublished - 31 Jan 2006

Keywords

  • Alboran Sea
  • Carboneras Fault zone
  • Seismicity
  • Strike-slip faulting
  • Submarine channels

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

Active faulting offshore SE Spain (Alboran Sea) : Implications for earthquake hazard assessment in the Southern Iberian Margin. / Gràcia, Eulàlia; Pallàs, Raimon; Soto, Juan Ignacio; Comas, Menchu; Moreno, Ximena; Masana, Eulàlia; Santanach, Pere; Diez, Susana; García, Margarita; Dañobeitia, Juanjo; Bartolomé, R.; Farrán, M.; Gómez, M.; Alpiste, M. J.R.; Lastras, G.; Wilmott, V.; Perea, H.; Blondel, P.; Gómez, O.; Bullock, L.; Jacobs, C.; Rouse, I.; White, D.; Whittle, S.; Terrinha, P.; Gafeira, J.; Roque, C.

In: Earth and Planetary Science Letters, Vol. 241, No. 3-4, 31.01.2006, p. 734-749.

Research output: Contribution to journalArticle

Gràcia, E, Pallàs, R, Soto, JI, Comas, M, Moreno, X, Masana, E, Santanach, P, Diez, S, García, M, Dañobeitia, J, Bartolomé, R, Farrán, M, Gómez, M, Alpiste, MJR, Lastras, G, Wilmott, V, Perea, H, Blondel, P, Gómez, O, Bullock, L, Jacobs, C, Rouse, I, White, D, Whittle, S, Terrinha, P, Gafeira, J & Roque, C 2006, 'Active faulting offshore SE Spain (Alboran Sea): Implications for earthquake hazard assessment in the Southern Iberian Margin', Earth and Planetary Science Letters, vol. 241, no. 3-4, pp. 734-749. https://doi.org/10.1016/j.epsl.2005.11.009
Gràcia, Eulàlia ; Pallàs, Raimon ; Soto, Juan Ignacio ; Comas, Menchu ; Moreno, Ximena ; Masana, Eulàlia ; Santanach, Pere ; Diez, Susana ; García, Margarita ; Dañobeitia, Juanjo ; Bartolomé, R. ; Farrán, M. ; Gómez, M. ; Alpiste, M. J.R. ; Lastras, G. ; Wilmott, V. ; Perea, H. ; Blondel, P. ; Gómez, O. ; Bullock, L. ; Jacobs, C. ; Rouse, I. ; White, D. ; Whittle, S. ; Terrinha, P. ; Gafeira, J. ; Roque, C. / Active faulting offshore SE Spain (Alboran Sea) : Implications for earthquake hazard assessment in the Southern Iberian Margin. In: Earth and Planetary Science Letters. 2006 ; Vol. 241, No. 3-4. pp. 734-749.
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AU - Gràcia, Eulàlia

AU - Pallàs, Raimon

AU - Soto, Juan Ignacio

AU - Comas, Menchu

AU - Moreno, Ximena

AU - Masana, Eulàlia

AU - Santanach, Pere

AU - Diez, Susana

AU - García, Margarita

AU - Dañobeitia, Juanjo

AU - Bartolomé, R.

AU - Farrán, M.

AU - Gómez, M.

AU - Alpiste, M. J.R.

AU - Lastras, G.

AU - Wilmott, V.

AU - Perea, H.

AU - Blondel, P.

AU - Gómez, O.

AU - Bullock, L.

AU - Jacobs, C.

AU - Rouse, I.

AU - White, D.

AU - Whittle, S.

AU - Terrinha, P.

AU - Gafeira, J.

AU - Roque, C.

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N2 - The southern margin of the Iberian Peninsula hosts the convergent boundary between the European and African Plates. The area is characterised by low to moderate magnitude shallow earthquakes, although large historical events have also occurred. In order to determine the possible sources of these events, we recently acquired swath-bathymetry, TOBI sidescan sonar and high-resolution seismic data on the Almería Margin (Eastern Alboran Sea). The new dataset reveals the offshore continuation of the NE-SW trending Carboneras Fault, a master fault in the Eastern Betic Shear Zone, and its associated structures (N150 and NS faults). These structures are active since they cut the Late Quaternary sedimentary units. The submarine Carboneras Fault zone is 100 km long, 5-10 km wide, and is divided into two N045 and N060 segments separated by an underlapping restraining stepover. Geomorphic features typically found in subaerial strike-slip faults, such as deflected drainage, water gaps, shutter ridges, pressure ridges and "en echelon" folds suggest a strike-slip motion combined with a vertical component along the submarine Carboneras Fault. Considering the NNW-SSE regional shortening axis, a left-lateral movement is deduced for the Carboneras Fault, whereas right-lateral and normal components are suggested for the associated N150 and NS faults, respectively. The offshore portion of this fault is at least twice as long as its onshore portion and together they constitute one of the longest structures in the southeastern Iberian Margin. Despite the fact that present day seismicity in the Almería margin seems to be associated with the N150 to NS faults, the Carboneras Fault is a potential source of large magnitude (Mw ∼7.2) events. Hence, the Carboneras Fault zone could pose a significant earthquake and tsunami hazard to the coasts of Spain and North Africa, and should therefore be considered in any hazard re-evaluation.

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KW - Seismicity

KW - Strike-slip faulting

KW - Submarine channels

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