Submarine landslide recurrence and links to seismicity on the Gorringe Bank Seamount, Offshore Portugal

2020 ◽  
Author(s):  
Davide Gamboa ◽  
Rachid Omira ◽  
Pedro Terrinha ◽  
Aldina Piedade
Keyword(s):  
Tsunami Hazard ◽  
Submarine Landslides ◽  
Close Link ◽  
Bathymetric Data ◽  
Tsunami Hazard Assessment ◽  
History Of ◽  
Funded Project ◽  
Gorringe Bank ◽  
Seismic Reflection Profiles ◽  
Northern Segment

<p>Submarine landslides are common features occurring on the flanks of seamounts. Often triggered by earthquakes or volcanic activity, such landslides are potential generators of tsunamis that constitute a dire geohazard for coastal communities. Understanding the recurrence history and geomorphology of seamount-flanking landslides and their link to seismic triggers is crucial for tsunami hazard assessment. This work aims at revealing the recurrence history of the landslides on the Gorringe Bank and their role on regional geohazards. Morphologically, the Gorringe Bank is the largest submarine seamount in Europe, with a length of circa 180 km and a height of 5000 m. It is linked to NW-directed thrusting which led to the exhumation of upper mantle lithologies in this major bathymetric structure. Numerous landslide scars are identified on both its northern and southern flanks, yet there is limited evidence of their presence and morphology on modern bathymetric data. A wealth of 2D seismic reflection profiles from offshore Southwest Portugal is here used to analyse the occurrence, timing and morphology of landslides complexes on the northwestern flank of the Gorringe Bank. A widespread frontal landslide complex of approximate Upper Miocene age is present along the whole flank, likely associated with the main phase of uplift. However, the recurrence of expressive submarine landslides in the Plio-Quarternary sequence is generally focused towards the northern segment of the Gorringe Bank. The geographical correlation between the areas of higher landslide number and clusters of seismicity epicentres suggest a close link between the two. This has direct implications for the assessment of landslide-prone locations on the seamount and to regional tsunami hazard models applicable to the Iberian and Northern African margins.</p><p>This work is supported by the FCT funded project MAGICLAND - MArine Geo-hazards InduCed by underwater LANDslides in the SW Iberian Margin (Ref: PTDC/CTA-GEO/30381/2017),</p>

scholarly journals Submarine landslides in the Santa Barbara Channel as potential tsunami sources

2006 ◽  
Vol 6 (1) ◽  
pp. 63-88 ◽  
Author(s):  
H. G. Greene ◽  
L. Y. Murai ◽  
P. Watts ◽  
N. A. Maher ◽  
M. A. Fisher ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Recent Sediment ◽  
Submarine Landslides ◽  
Santa Barbara ◽  
Santa Barbara Basin ◽  
Northern Flank ◽  
Bathymetric Data ◽  
Fluid Seepage ◽  
Slide Debris ◽  
Seismic Reflection Profiles

Abstract. Recent investigations using the Monterey Bay Aquarium Research Institutes (MBARI) Remotely Operated Vehicles (ROVs) "Ventana" and "Tiburon" and interpretation of MBARI's EM 300 30 kHz multibeam bathymetric data show that the northern flank of the Santa Barbara Basin has experienced massive slope failures. Of particular concern is the large (130 km2) Goleta landslide complex located off Coal Oil Point near the town of Goleta, that measures 14.6-km long extending from a depth of 90 m to nearly 574 m deep and is 10.5 km wide. We estimate that approximately 1.75 km3 has been displaced by this slide during the Holocene. This feature is a complex compound submarine landslide that contains both surfical slump blocks and mud flows in three distinct segments. Each segment is composed of a distinct head scarp, down-dropped head block and a slide debris lobe. The debris lobes exhibit hummocky topography in the central areas that appear to result from compression during down slope movement. The toes of the western and eastern lobes are well defined in the multibeam image, whereas the toe of the central lobe is less distinct. Continuous seismic reflection profiles show that many buried slide debris lobes exist and comparison of the deformed reflectors with ODP Drill Site 149, Hole 893 suggest that at least 200 000 years of failure have occurred in the area (Fisher et al., 2005a). Based on our interpretation of the multibeam bathymetry and seismic reflection profiles we modeled the potential tsunami that may have been produced from one of the three surfical lobes of the Goleta slide. This model shows that a 10 m high wave could have run ashore along the cliffs of the Goleta shoreline. Several other smaller (2 km2 and 4 km2) slides are located on the northern flank of the Santa Barbara Basin, both to the west and east of Goleta slide and on the Conception fan along the western flank of the basin. One slide, named the Gaviota slide, is 3.8 km2, 2.6 km long and 1.7 km wide. A distinct narrow scar extends from near the eastern head wall of this slide for over 2km eastward toward the Goleta slide and may represent either an incipient failure or a remnant of a previous failure. Push cores collected within the main head scar of this slide consisted of hydrogen sulfide bearing mud, possibly suggesting active fluid seepage and a vibra-core penetrated ~50 cm of recent sediment overlying colluvium or landslide debris confirming the age of ~300 years as proposed by Lee et al. (2004). However, no seeps or indications of recent movement were observed during our ROV investigation within this narrow head scar indicating that seafloor in the scar is draped with mud.

scholarly journals The 1755 Lisbon Tsunami at Vila do Bispo Municipality, Portugal

2015 ◽  
Vol 10 (6) ◽  
pp. 1067-1080 ◽  
Author(s):  
Angela Santos ◽  
◽  
Shunichi Koshimura ◽  
Keyword(s):  
Numerical Model ◽  
Historical Data ◽  
Source Area ◽  
Tsunami Hazard ◽  
Tsunami Source ◽  
Historical Event ◽  
Natural Landscape ◽  
Field Surveys ◽  
Tsunami Hazard Assessment ◽  
Gorringe Bank

The numerical model of the 1755 Lisbon Tsunami was conducted at Vila do Bispo municipality. The tsunami source area of this historical event is assumed to be on the Gorringe Bank. Numerical model results of historical data have been validated by a combined analysis of eyewitnesses’ accounts, field surveys, geological records and archeological findings (conducted by previous authors). The coastal area has remained a mostly natural landscape since the 18thcentury, with popular beaches that increase the population potentially exposed to a tsunami, especially one occurring in summer. For these reasons, we use local tsunami hazard assessment as a criterion varying between moderate and critical. Results also show that the 16 low ground areas we surveyed were inundated between 15 and 30 minutes after the earthquake. For this reason, persons should act quickly in future to evacuate areas immediately after an earthquake and to move to higher ground. Results also show that safe, swift evacuation may be difficult in 50% of these areas, endangering special populations such as tourists. Tsunami information boards should therefore be put on beaches and evacuation exercises and drills should be implemented and practiced regularly.

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

2015 ◽  
Vol 15 (11) ◽  
pp. 2557-2568 ◽  
Author(s):  
M. Wronna ◽  
R. Omira ◽  
M. A. Baptista
Keyword(s):  
Sea Level ◽  
Wave Height ◽  
Hazard Assessment ◽  
Test Site ◽  
Tsunami Hazard ◽  
Deterministic Approach ◽  
Flow Depth ◽  
Mean Sea Level ◽  
Tsunami Hazard Assessment ◽  
The Impact

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 deep-water ports, which has oil-bearing, petrochemical, liquid-bulk, 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 km2.

Generating Random Earthquake Events for Probabilistic Tsunami Hazard Assessment

2016 ◽  
Vol 173 (12) ◽  
pp. 3671-3692 ◽  
Author(s):  
Randall J. LeVeque ◽  
Knut Waagan ◽  
Frank I. González ◽  
Donsub Rim ◽  
Guang Lin
Keyword(s):  
Hazard Assessment ◽  
Tsunami Hazard ◽  
Tsunami Hazard Assessment ◽  
Probabilistic Tsunami Hazard Assessment

Submarine Landslides and Their Tsunami Hazard

2016 ◽  
Vol 49 (1) ◽  
Author(s):  
David R. Tappin
Keyword(s):  
Papua New Guinea ◽  
New Guinea ◽  
Submarine Landslide ◽  
Tsunami Hazard ◽  
Publication Date ◽  
Submarine Landslides ◽  
Critical Importance ◽  
Grand Banks ◽  
Landslide Mechanisms ◽  
Landslide Tsunamis

Most tsunamis are generated by earthquakes, but in 1998, a seabed slump offshore of northern Papua New Guinea (PNG) generated a tsunami up to 15 m high that killed more than 2,200 people. The event changed our understanding of tsunami mechanisms and was forerunner to two decades of major tsunamis that included those in Turkey, the Indian Ocean, Japan, and Sulawesi and Anak Krakatau in Indonesia. PNG provided a context to better understand these tsunamis as well as older submarine landslide events, such as Storegga (8150 BP); Alika 2 in Hawaii (120,000 BP), and Grand Banks, Canada (1929), together with those from dual earthquake/landslide mechanisms, such as Messina (1908), Puerto Rico (1928), and Japan (2011). PNG proved that submarine landslides generate devastating tsunamis from failure mechanisms that can be very different, whether singly or in combination with earthquakes. It demonstrated the critical importance of seabed mapping to identify these mechanisms as well as stimulated the development of new numerical tsunami modeling methodologies. In combination with other recent tsunamis, PNG demonstrated the critical importance of these events in advancing our understanding of tsunami hazard and risk. This review recounts how, since 1998, understanding of the tsunami hazard from submarine landslides has progressed far beyond anything considered possible at that time. ▪ For submarine landslide tsunamis, advances in understanding take place incrementally, usually in response to major, sometimes catastrophic, events. ▪ The Papua New Guinea tsunami in 1998, when more than 2,200 people perished, was a turning point in first recognizing the significant tsunami hazard from submarine landslides. ▪ Over the past 2 to 3 years advances have also been made mainly because of improvements in numerical modeling based on older tsunamis such as Grand Banks in 1929, Messina in 1908, and Storegga at 8150 BP. ▪ Two recent tsunamis in late 2018, in Sulawesi and Anak Krakatau, Indonesia, where several hundred people died, were from very unusual landslide mechanisms—dual (strike-slip and landslide) and volcanic collapse—and provide new motivations for understanding these tsunami mechanisms. ▪ This is a timely, state of the art review of landslide tsunamis based on recent well-studied events and new research on older ones, which provide an important context for the recent tsunamis in Indonesia in 2018. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 49 is May 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Regional tsunami hazard maps for the Far East coast of the Russian Federation built in the framework of the PTHA methodology

2019 ◽  
pp. 55-72
Author(s):  
Вячеслав Константинович Гусяков ◽  
Владимир Андреевич Кихтенко ◽  
Леонид Борисович Чубаров ◽  
Юрий Иванович Шокин
Keyword(s):  
Russian Federation ◽  
Hazard Assessment ◽  
East Coast ◽  
Far East ◽  
Tsunami Hazard ◽  
Eastern Coast ◽  
The Far East ◽  
Tsunami Hazard Assessment ◽  
The Russian Federation ◽  
Probabilistic Tsunami Hazard Assessment

В работе идет речь о реализации методики вероятностного цунамирайонирования побережья, известной под названием PTHA (Probabilistic Tsunami Hazard Assessment), для создания обзорных карт цунамиопасности дальневосточного побережья России. Обсуждаются методологические основы такого подхода, проблемы построения сейсмотектонических моделей основных цунамигенных зон, численные методики получения расчетных каталогов высот волн на побережье. Приведены примеры обзорных карт для различных повторяемостей, построенных с применением методики PTHA и представленных с помощью созданного веб-приложения WTMap. Упоминаются также некоторые проблемы применения методики PTHA, связанные как с недостаточностью данных наблюдений, так и со сложностью выполнения большого объема сценарного численного моделирования. The article describes the results of the implementation of the PTHA (Probabilistic Tsunami Hazard Assessment) methodology for creating the overview maps of tsunami hazard for the Far East coast of the Russian Federation. Such maps show the characteristics of the catastrophic impact of tsunami waves on the coast and the probability of their exceeding in a given period of time. The methodological basis of the PTHA approach to the assessment of tsunami hazard, the problems of constructing seismotectonic models of the main tsunamigenic zones, mathematical models and algorithms for calculating probability estimates of tsunami danger are discussed. The version of the PTHA methodology outlined in the article is implemented as a “WTmap” Web-application that has an access to the entire observational information related to coastal tsunami zoning and software packages used. The application allows to obtain the estimates of the expected tsunami heights and their recurrence estimates and to map them on specific parts of the Far Eastern coast of the Russian Federation. The obtained estimates can be quickly recalculated when replacing the observational catalogs with more complete and reliable ones, with the addition of new, previously absent events or the revision of their parameters, as well as the results of new scenario calculations. Examples of overview maps for various recurrence intervals, constructed using the PTHA methodology and presented using the “WTMap” application, are given. Some problems of using the PTHA methodology related to the lack of available observational data and to the complexity of performing a large amount of scenario simulations are also discussed.

scholarly journals Storia di un antifascista siciliano, professore di lingue classiche: Carmelo Salanitro (Adrano, 1894 – Mauthausen, 1945) = History of a Sicilian antifascist, professor of classics: Carmelo Salanitro (Adrano, 1894 – Mauthausen, 1945)

ΠΗΓΗ/FONS ◽  
2019 ◽  
Vol 3 (1) ◽  
pp. 103
Author(s):  
Gian Franco Gianotti
Keyword(s):  
Second World War ◽  
European History ◽  
Recent Book ◽  
World War ◽  
Close Link ◽  
Italian School ◽  
Classical Studies ◽  
History Of ◽  
Second World

Resumen: Basado en el análisis de un libro reciente (Pietro Scalisi, L’onore e la viltà. In Memoria di Carmelo Salanitro Martire del Libero Pensiero, 2016), el artículo recorre la vida y el legado de Carmelo Salanitro, un antifascista siciliano condenado por la dictadura italiana y muerto en un campo de exterminio alemán. En la biografía de Salanitro se destaca el estrecho vínculo entre los estudios clásicos, la enseñanza de latín y griego y la búsqueda de la libertad: una relación ejemplar en la historia europea de la primera mitad del siglo XX.Palabras clave: Carmelo Salanitro, antifascismo, Segunda Guerra Mundial, idiomas clásicos, escuela italiana.Abstract: Based on a recent book (Pietro Scalisi, L’onore e la viltà. In Memoria di Carmelo Salanitro Martire del Libero Pensiero, 2016), the article traces the life and the witness of freedom of Carmelo Salanitro, a Sicilian anti-fascist condemned by the Italian dictatorship and died in a German extermination camp. In the biography of Salanitro stands out the close link between classical studies, teaching of Latin and Greek and the pursuit of freedom: an exemplary relationship in the European history of the first half of the 20th century.Keywords: Carmelo Salanitro, Anti-fascism, Second World War, Classical languages, Italian school.

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