Probabilistic Tsunami Hazard in the Northeast Atlantic from Near- and Far-Field Tectonic Sources

Nat. Hazards Earth Syst. Sci.

2015

Self Cite

Abstract. In this paper, we present a deterministic approach to tsunami hazard assessment for the city and harbour of Sines, Portugal, one of the test sites of project ASTARTE (Assessment, STrategy And Risk Reduction for Tsunamis in Europe). Sines has one of the most important deepwater ports, which has oil-bearing, petrochemical, liquidbulk, coal, and container terminals. The port and its industrial infrastructures face the ocean southwest towards the main seismogenic sources. This work considers two different seismic zones: the Southwest Iberian Margin and the Gloria Fault. Within these two regions, we selected a total of six scenarios to assess the tsunami impact at the test site. The tsunami simulations are computed using NSWING, a Non-linear Shallow Water model wIth Nested Grids. In this study, the static effect of tides is analysed for three different tidal stages: MLLW (mean lower low water), MSL (mean sea level), and MHHW (mean higher high water). For each scenario, the tsunami hazard is described by maximum values of wave height, flow depth, drawback, maximum inundation area and run-up. Synthetic waveforms are computed at virtual tide gauges at specific locations outside and inside the harbour. The final results describe the impact at the Sines test site considering the single scenarios at mean sea level, the aggregate scenario, and the influence of the tide on the aggregate scenario. The results confirm the composite source of Horseshoe and Marques de Pombal faults as the worst-case scenario, with wave heights of over 10 m, which reach the coast approximately 22 min after the rupture. It dominates the aggregate scenario by about 60 % of the impact area at the test site, considering maximum wave height and maximum flow depth. The HSMPF scenario inundates a total area of 3.5 km 2 .

Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Deterministic approach for multiple-source tsunami hazard assessment for Sines, Portugal

Wronna

Omira

Nat. Hazards Earth Syst. Sci.

2015

Self Cite

“…These two subsegments might correspond to the reactivation of previous transform faults associated with the Mid-Atlantic Ridge; the northern segment follows the shape of the Gloria Fault, and the southern segment corresponds to the most probable location of the 26 May 1975 event (Lynnes andRuff, 1985, andKaabouben et al, 2008). In this study, we assume that the coseismic displacement can be described by the half space elastic approach following Okada (1985). We use nine independent parameters: fault width W , fault length L, fault azimuth (strike) ϕ, dip angle δ, average slip along the fault u, slip angle (rake) λ, and depth below seafloor h to describe each seismic event of the synthetic catalogue.…”

Section: Plate Kinematic Contextmentioning

confidence: 99%

“…In situations where the effects of smaller tsunami events are also important (e.g. interaction with harbours or other coastal structures), probabilistic hazard assessments can give a better insight into expected amplitudes and recurrence times (Geist and Parsons, 2006;Power et al, 2007;González et al, 2009;Sørensen et al, 2012;Omira et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

“…We consider the simplest case of a rectangular fault with constant slip because of the location of the Gloria Fault in relation to the points of interest (POIs), and we use scaling laws to infer the fault parameters. These parameters are then used to compute the seafloor deformation using the half space elastic approach (Okada, 1985). Assuming the incompressibility of the seawater, we can directly transfer the sea bottom deformation to the water surface and use it as the initial condition for the tsunami propagation and use standard shallow water numerical modelling to provide an accurate assessment of the potential impacts close to the coasts.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Synthetic tsunami waveform catalogs with kinematic constraints

Nat. Hazards Earth Syst. Sci.

Miranda

Matias

et al. 2017

Abstract. In this study we present a comprehensive methodology to produce a synthetic tsunami waveform catalogue in the northeast Atlantic, east of the Azores islands. The method uses a synthetic earthquake catalogue compatible with plate kinematic constraints of the area. We use it to assess the tsunami hazard from the transcurrent boundary located between Iberia and the Azores, whose western part is known as the Gloria Fault. This study focuses only on earthquakegenerated tsunamis. Moreover, we assume that the time and space distribution of the seismic events is known. To do this, we compute a synthetic earthquake catalogue including all fault parameters needed to characterize the seafloor deformation covering the time span of 20 000 years, which we consider long enough to ensure the representability of earthquake generation on this segment of the plate boundary. The computed time and space rupture distributions are made compatible with global kinematic plate models. We use the tsunami empirical Green's functions to efficiently compute the synthetic tsunami waveforms for the dataset of coastal locations, thus providing the basis for tsunami impact characterization. We present the results in the form of offshore wave heights for all coastal points in the dataset.Our results focus on the northeast Atlantic basin, showing that earthquake-induced tsunamis in the transcurrent segment of the Azores-Gibraltar plate boundary pose a minor threat to coastal areas north of Portugal and beyond the Strait of Gibraltar. However, in Morocco, the Azores, and the Madeira islands, we can expect wave heights between 0.6 and 0.8 m, leading to precautionary evacuation of coastal areas. The advantages of the method are its easy application to other regions and the low computation effort needed.

Probabilistic Tsunami Hazard Analysis: Multiple Sources and Global Applications

Grezio

Babeyko²,

et al. 2017

Reviews of Geophysics

210

165

Applying probabilistic methods to infrequent but devastating natural events is intrinsically challenging. For tsunami analyses, a suite of geophysical assessments should be in principle evaluated because of the different causes generating tsunamis (earthquakes, landslides, volcanic activity, meteorological events, and asteroid impacts) with varying mean recurrence rates. Probabilistic Tsunami Hazard Analyses (PTHAs) are conducted in different areas of the world at global, regional, and local scales with the aim of understanding tsunami hazard to inform tsunami risk reduction activities. PTHAs enhance knowledge of the potential tsunamigenic threat by estimating the probability of exceeding specific levels of tsunami intensity metrics (e.g., run‐up or maximum inundation heights) within a certain period of time (exposure time) at given locations (target sites); these estimates can be summarized in hazard maps or hazard curves. This discussion presents a broad overview of PTHA, including (i) sources and mechanisms of tsunami generation, emphasizing the variety and complexity of the tsunami sources and their generation mechanisms, (ii) developments in modeling the propagation and impact of tsunami waves, and (iii) statistical procedures for tsunami hazard estimates that include the associated epistemic and aleatoric uncertainties. Key elements in understanding the potential tsunami hazard are discussed, in light of the rapid development of PTHA methods during the last decade and the globally distributed applications, including the importance of considering multiple sources, their relative intensities, probabilities of occurrence, and uncertainties in an integrated and consistent probabilistic framework.