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Research Project
Assessment, STrategy And Risk Reduction for Tsunamis in Europe
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Tsunami characteristics along the Peru-Chile trench: analysis of the 2015 Mw8.3 Illapel, the 2014 Mw8.2 iquique and the 2010 Mw8.8 maule tsunamis in the near-field
Publication . Omira, Rachid; Baptista, Maria Ana Carvalho Viana; Lisboa, F.
Tsunamis occur quite frequently following large magnitude earthquakes along the Chilean coast. Most of these earthquakes occur along the Peru-Chile Trench, one of the most seismically active subduction zones of the world. This study aims to understand better the characteristics of the tsunamis triggered along the Peru-Chile Trench. We investigate the tsunamis induced by the Mw8.3 Illapel, the Mw8.2 Iquique and the Mw8.8 Maule Chilean earthquakes that happened on September 16th, 2015, April 1st, 2014 and February 27th, 2010, respectively. The study involves the relation between the co-seismic deformation and the tsunami generation, the near-field tsunami propagation, and the spectral analysis of the recorded tsunami signals in the near-field. We compare the tsunami characteristics to highlight the possible similarities between the three events and, therefore, attempt to distinguish the specific characteristics of the tsunamis occurring along the Peru-Chile Trench. We find that these three earthquakes present faults with important extensions beneath the continent which result in the generation of tsunamis with short wavelengths, relative to the fault widths involved, and with reduced initial potential energy. In addition, the presence of the Chilean continental margin, that includes the shelf of shallow bathymetry and the continental slope, constrains the tsunami propagation and the coastal impact. All these factors contribute to a concentrated local impact but can, on the other hand, reduce the far-field tsunami effects from earthquakes along Peru-Chile Trench.
On the construction and use of a Paleo-DEM to reproduce tsunami inundation in a historical urban environment: the case of the 1755 Lisbon tsunami in Cascais
Publication . Wronna, Martin; Baptista, Maria Ana Carvalho Viana; Götz, Joachim
In this study, we present a methodology to reconstruct a Paleo Digital Elevation Model (PDEM) to simulate the propagation of a tsunami similar to the one that occurred on the 1st November 1755 in Cascais, Portugal. The method combines historical data, GPS-measurements, and presentday topographic data to build the PDEM. Antique maps were geo-referenced and altitudinal information was reconstructed using historic descriptions. We used old documents to estimate the original landscape of several sites. Analyses and interpretation of these sources of information served to attribute and approximate elevations of both geomorphologic landforms and building features. We used antique maps to rebuild the boundaries of old river mouths and water courses. Finally, we use GPS-RTK to implement obtained elevation data along creek mouths to interpolate in channelled areas to get their slope. Using this methodology and a numerical tsunami simulation code, we reproduced a 1st November 1755-like flooding in Cascais, Portugal. Our results show that using the PDEM, we can reproduce the inundation described in all of the historical accounts.
On the source of the 8 May 1939 Azores earthquake - tsunami observations and numerical modelling
Publication . Reis, Cláudia; Omira, Rachid; Matias, Luis; Baptista, Maria Ana Carvalho Viana
On 8 May 1939, an earthquake (Ms7.1) occurred near the Azores archipelago, with an epicentre located close to the western end of the Gloria fault. Previous studies present different epicentre locations spreading over a large area, and two different types of focal mechanisms. Given these uncertainties, the interpretation of the seismological information in a complex tectonic environment between the Gloria Fault and the Terceira Ridge is a matter of debate. The event caused a small tsunami recorded in the Azores Islands. In this study, we use the tsunami observations and tsunami numerical modelling to select the earthquake fault rupture that best fits the tsunami observations. We consider the different focal mechanism solutions, perform tsunami numerical modelling, and compute synthetic tsunami waveforms at the tide gauge locations. We find that an earthquake caused by a low-angle dipping fault with dominant strike-slip movement generates a tsunami that reproduces well the record at Ponta Delgada tide gauge. Finally, in areas where earthquakes are rare, the study of ancient earthquakes must use all information available, namely tsunami observations and mareograph data.
The Tagus River delta landslide, off Lisbon, Portugal. Implications for Marine geo-hazards
Publication . Terrinha, Pedro; Duarte, Henrique; Brito, Pedro; Noiva, João; Ribeiro, Carlos; Omira, Rachid; Baptista, Maria Ana Carvalho Viana; Miranda, Miguel; Magalhaes, Vitor; Roque, C.; Rosa, Marcos; Alves, Paulo; Teixeira, Francisco; Tagusdelta Cruise Team
The stratigraphy of the Tagus river ebb-tidal delta off Lisbon (Portugal) is investigated using high resolution multichannel seismic reflection profiles with the purpose of searching for sedimentary or erosive features associated with landslides. The Tagus delta is sub-divided in two prograding seismic units of 17 ky to 13 ky and 13 ky to Present based on the calibration of seismic lines using gravity and box-cores in the Tagus pro-delta. We report the existence of a buried landslide with 11 km of length, 3.5 km of width and a maximum thickness of 20 m that accounted for the collapse of half of the upper unit of the Tagus river delta front in Holocene times. The non-collapsed half of the delta front contains extensive shallow gas of still unknown origin and nature. An estimated age of similar to 8 ky BP for the Tagus delta landslide is proposed based on stratigraphic correlation. The trigger mechanisms of the newly identified Tagus landslide are discussed as well as of the several landslides also found in the lower delta unit. These findings present a first step towards a future assessment of the susceptibility of the nearby coastal areas and the off-shore infrastructures to hazards related to such large collapses.
Exploring offshore sediment evidence of the 1755 CE tsunami (Faro, Portugal): implications for the study of outer shelf tsunami deposits
Publication . Kümmerer, Vincent; Drago, Teresa; Veiga-Pires, C.; Silva, Pedro; Magalhaes, Vitor; Mena, Anxo; Lopes, Ana; Rodrigues, Ana Isabel; Schmidt, Sabine; Terrinha, Pedro; Baptista, Maria Ana
Outer shelf sedimentary records are promising for determining the recurrence intervals of tsunamis. However, compared to onshore deposits, offshore deposits are more difficult to access, and so far, studies of outer shelf tsunami deposits are scarce. Here, an example of studying these deposits is presented to infer implications for tsunami-related signatures in similar environments and potentially contribute to pre-historic tsunami event detections. A multidisciplinary approach was performed to detect the sedimentary imprints left by the 1755 CE tsunami in two cores, located in the southern Portuguese continental shelf at water depths of 58 and 91 m. Age models based on C-14 and Pb-210(xs) allowed a probable correspondence with the 1755 CE tsunami event. A multi-proxy approach, including sand composition, grain-size, inorganic geochemistry, magnetic susceptibility, and microtextural features on quartz grain surfaces, yielded evidence for a tsunami depositional signature, although only a subtle terrestrial signal is present. A low contribution of terrestrial material to outer shelf tsunami deposits calls for methodologies that reveal sedimentary structures linked to tsunami event hydrodynamics. Finally, a change in general sedimentation after the tsunami event might have influenced the signature of the 1755 CE tsunami in the outer shelf environment.
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Funding agency
European Commission
Funding programme
FP7
Funding Award Number
603839