High-resolution imaging of submarine large seismogenic and tsunamigenic structures in the SW Iberian Margin: new insights from insight survey (2018)

Abstract

Large earthquakes, submarine landslides and their occasional tsunami originated are geohazards of great societal concern because of the impact on the world economies and coastal populations. Dramatic examples of such events include the 2004 northern Sumatra and 2011 Tohoku earthquakes and tsunamis. However, earthquakes of magnitude > 7.0 in areas of relatively slow tectonic deformation and with long recurrence intervals, such as the external part of the Gulf of Cadiz, might also have a significant impact as the well-known case of the destructive 1755 Lisbon earthquake, related submarine landslides, and resulting tsunami. Although the Gulf of Cadiz is one of the highest geohazard zones in Europe, we currently lack appropriate understanding of both the rupture areas and stress-state of the faults and sediments in which such catastrophic events originated. The relatively great water depths, poor accuracy on the location of moderate-to¬-high magnitude earthquakes, lack of understanding of subsurface hydrology and the few constraints on ages of the sedimentary sequences hinder an appropriate understanding of location and characteristics of earthquake ruptures and associated submarine landslides in the Gulf of Cadiz. Our hypothesis is that such understanding can only be developed by using ultra-high resolution (UHR) tools capable of providing the characterization of faults, submarine landslides, and fluid escape structures while being able to work in deep waters such as those of the external Gulf of Cadiz. INSIGHT tackles this problem by using state-of ¬the-art UHR techniques such as microbathymetry, 2D high-resolution seismic data, and sampling using piston cores. We aim at 1) Map in detail the active faults with largest seismogenic potential, 2) Accurately determine the seismic parameters of these faults, 3) Characterize associated submarine landslides, 4) Assess the likelihood of recent submarine landslides activation, and finally, 5) Evaluate the seismogenic and tsunamigenic potential of the largest tectonic sources