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

Terrinha, Pedro; Pinheiro, Luís Menezes; Henriet, J.-P.; Matias, L.; Ivanov, M.K.; Monteiro, Jose Hyppolito; Akhmetzhanov, A.; Volkonskaya, A.; Cunha, T. A.; Shaskin, P.; Rovere, Marzia

doi:10.1016/s0025-3227(02)00682-5

Cited by 140 publications

(93 citation statements)

References 11 publications

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“…The northernmost segment is offset by a WNW-ESE wrench fault. Mass wasting deposits associated with the uplift are also visible, such as, debris flow deposits and ridges that correspond to turbidity levees (Gràcia et al, 2003;Terrinha et al, 2003). This is the most relevant active structure mapped in the SW Iberian area and was proposed as the source of the 1755 event.…”

Section: Tsunamigenic Source Areasmentioning

confidence: 99%

Revision of the Portuguese catalog of tsunamis

Baptista

Miranda

2009

Nat. Hazards Earth Syst. Sci.

165

111

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Abstract. Catastrophic tsunamis are described in historical sources for all regions around the Gulf of Cadiz, at least since 60 BC. Most of the known events are associated with moderate to large earthquakes and among them the better studied is 1 November 1755. We present here a review of the events which effects, on the coasts of the Portuguese mainland and Madeira Island, are well described in historical documents or have been measured by tide gauges since the installation of these instruments. For a few we include new relevant information for the assessment of the tsunami generation or effects, and we discard events that are included in existing compilations but are not supported by quality historical sources or instrumental records. We quote the most relevant quantitative descriptions of tsunami effects on the Portuguese coast, including in all pertinent cases a critical review of the coeval sources, to establish a homogenous event list. When available, instrumental information is presented. We complement all this information with a summary of the conclusions established by paleo-tsunami research.

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Section: Tsunamigenic Source Areasmentioning

confidence: 99%

Revision of the Portuguese catalog of tsunamis

Baptista

Miranda

2009

Nat. Hazards Earth Syst. Sci.

165

111

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“…Recently, however, drill core and seismic profile data suggest an incipient subduction area west of Portugal where the tsunami origin may possibly have been located ( Baptista et al, 1998;Zitellini et al, 1999Zitellini et al, , 2001. Data from off-shore southern Portugal revealed a number of active faults that may represent an earthquake and tsunami hazard to the coast of SW Iberia and NW Africa (Gracia et al, 2003a(Gracia et al, , b, 2010Terrinha et al, 2003;Zitellini et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Holocene palaeotsunami catalogue of SW Iberia

Lario

Cardeña

Goy

et al. 2011

Quaternary International

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Many on-shore studies focused on high energy marine events occurred in the Gulf of Cadiz have been published since the 1990s. Most of the findings came from sedimentary, palaeontological and geomor phological records on estuaries, marshes, beach-barriers (spit-bars), and some coastal lowlands. Recent off-shore investigations in SW Iberia considered turbidite deposits as a proxy to recognise palae oearthquakes in this zone. The comparison of datasets from both on-shore and off-shore records indicate that at least five tsunami events generated by strong earthquakes affected this area during the last 7000 years, previous to the more recent and well-documented 1755 AD Lisbon earthquake tsunami event. The catalogue of Holocene palaeotsunami presented here is supported by geological and geomorphological evidences, but also for archaeoseismic and palaeoseismic evidence and written reports for the more recent events occurred during historical times. The recurrence interval for these catastrophic events can be bracketed between 1200 and 1500 years.

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“…The problem of epicentral location has been addressed by various early studies (Reid 1914;Pereira de Sousa 1919), and since the beginning of the instrumental period, a consensus has attributed the origin of the earthquake to a structure located between the Gorringe Bank and the Coral Patch Ridge (Machado 1966;Moreira 1985;Johnston 1996;Grandin et al 2007b;Barkan et al 2009). In the most recent hypothesis, Grandin et al (2007b) tested, by forward modelling, three published sources for the 1755 earthquake that can be considered as end-members of the set of proposed offshore seismic sources (Johnston 1996;Zitellini et al 2001;Terrinha et al 2003;Gutscher et al 2002;Gutscher et al 2006;Thiebot and Gutscher 2006). Following the results of these tests, Grandin et al (2007b) concluded that a fault located below Gorringe Bank, with a rupture directed towards the SW, reproduces the overall pattern of macroseismic observations better than a fault aligned along the Marquês de Pombal-Pereira de Sousa Fault zone or a subduction-related thrust fault in the Gulf of Cádiz.…”

Section: Ground Motion Simulations and Earthquake Sourcementioning

confidence: 99%

Ground motion simulations of the SW Iberia margin: rupture directivity and earth structure effects

2011

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In this study, we focus on the region between Gorringe Bank and the Horseshoe Fault located in the SW Iberia margin, which is believed to be the site of the great 1755 earthquake. We model ground motions using an extended source located near the Horseshoe scarp to generate synthetic waveforms using a wave propagation code, based on the finite-difference method. We compare the simulated waveforms, for the Algarve Basin and the Lower Tagus Valley Basin (Portugal), using a 3-D velocity model down to the Moho discontinuity with a simple 1-D layered model. The radiated wave field is very sensitive to the velocity model and a small number of source parameters, in particular, the rupture directivity. The rupture directivity, the strike direction and the fault dimensions are critical to the azimuthal distribution of the maximum amplitude oscillations. We show that the use of a stratified 1-D model is inappropriate in SW Iberia, where sources are located in the oceanic domain and receivers in the continental domain. The crustal structure varies dramatically along the ray paths, with large-scale heterogeneities of low or high velocities. Moreover, combined with the geometric limitations inherent to the region, a strong tradeoff between several parameters is often observed; this is particularly critical when studying moderate magnitude earthquakes (M \ 6), which constitute the bulk of the seismic catalogue in SW Iberia.

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

Cited by 140 publications

References 11 publications

Revision of the Portuguese catalog of tsunamis

Revision of the Portuguese catalog of tsunamis

Holocene palaeotsunami catalogue of SW Iberia

Ground motion simulations of the SW Iberia margin: rupture directivity and earth structure effects

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