Articles | Volume 12, issue 10
Nat. Hazards Earth Syst. Sci., 12, 3151–3168, 2012

Special issue: Marine and lake paleoseismology

Nat. Hazards Earth Syst. Sci., 12, 3151–3168, 2012

Research article 23 Oct 2012

Research article | 23 Oct 2012

Quaternary active tectonic structures in the offshore Bajo Segura basin (SE Iberian Peninsula – Mediterranean Sea)

H. Perea1,2, E. Gràcia2, P. Alfaro3, R. Bartolomé2, C. Lo Iacono2, X. Moreno2, E. Masana4, and EVENT-SHELF Team* H. Perea et al.
  • 1LATTEX – IDL, GeoFCUL, Universidade de Lisboa, Ed.C6, Campo Grande 1749-016 Lisbon, Portugal
  • 2Unitat de Tecnologia Marina – CSIC, Centre Mediterrani d'Investigacions Marines i Ambientals, Psg. Marítim de la Barceloneta, 37–49, 08003, Barcelona, Spain
  • 3Dept. de Ciencias de la Tierra y del Medio Ambiente, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain
  • 4RISKNAT, Dept. Geodinàmica i Geofísica, Universitat de Barcelona, Martí Franqués, s/n, 08028 Barcelona, Spain
  • *M. Farran (ICM-CSIC), E. Andara (IGME), S. Pérez and M. Román Alpiste (UG)

Abstract. The Bajo Segura fault zone (BSFZ) is the northern terminal splay of the Eastern Betic shear zone (EBSZ), a large left-lateral strike-slip fault system of sigmoid geometry stretching more than 450 km from Alicante to Almería. The BSFZ extends from the onshore Bajo Segura basin further into the Mediterranean Sea and shows a moderate instrumental seismic activity characterized by small earthquakes. Nevertheless, the zone was affected by large historical earthquakes of which the largest was the 1829 Torrevieja earthquake (IEMS98 X). The onshore area of the BSFZ is marked by active transpressive structures (faults and folds), whereas the offshore area has been scarcely explored from the tectonic point of view. During the EVENT-SHELF cruise, a total of 10 high-resolution single-channel seismic sparker profiles were obtained along and across the offshore Bajo Segura basin. Analysis of these profiles resulted in (a) the identification of 6 Quaternary seismo-stratigraphic units bounded by five horizons corresponding to regional erosional surfaces related to global sea level lowstands; and (b) the mapping of the active sub-seafloor structures and their correlation with those described onshore. Moreover, the results suggest that the Bajo Segura blind thrust fault or the Torrevieja left-lateral strike-slip fault, with prolongation offshore, could be considered as the source of the 1829 Torrevieja earthquake. These data improve our understanding of present deformation along the BSFZ and provide new insights into the seismic hazard in the area.