Impact of seismicity on Nice slope stability—Ligurian Basin, SE France: a geotechnical revisit

Roesner, Alexander; Wiemer, Gauvain; Kreiter, Stefan; Wenau, Stefan; Wu, Ting-Wei; Courboulex, Françoise; Spieß, V.; Kopf, Achim J

doi:10.1007/s10346-018-1060-7

Cited by 15 publications

(5 citation statements)

References 59 publications

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“…To what extent can a site effect be dangerous for airport zone stability? Roesner et al (2019) recently attempted to answer this question. They thought that the site effect at the airport should be the same as that obtained at a station located on soft sediments west of Nice, the NALS station, (see its location of Fig.…”

Section: Discussionmentioning

confidence: 99%

Strong Site Effect Revealed by a New Broadband Seismometer on the Continental Shelf Offshore Nice Airport (Southeastern France)

Courboulex

Mercerat²,

Deschamps

et al. 2020

Pure Appl. Geophys.

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A broadband seismological station (PRIMA) installed offshore Nice airport (southeastern France) reveals a strong amplification effect of seismic waves. PRIMA station was in operation for 2 years (9/2016 to 10/2018) on the outer shelf at a water depth of 18 m. Situated at the mouth of the Var River, this zone is unstable and prone to landslides. A catastrophic landslide and tsunami already occurred in 1979, causing 10 casualties. Given the level of seismicity of the area, it is important to infer the impact of an earthquake on this zone. We analyze the recordings of earthquakes and seismic noise at the PRIMA station by comparing them to nearby inland stations. We find that the seismic waves are strongly amplified at PRIMA at some specific frequencies (with an amplification factor greater than 10 at 0.9 Hz). Using geological and geophysical data, we show that the main amplification frequency peak (at 0.9 Hz) is due to the velocity contrast between the Pliocene sedimentary layer and fine-grained sediments dated from the Holocene, at about 100 m depth. This velocity contrast is also present along the Var valley, but the level of amplification detected on PRIMA station is larger. Using numerical simulations of seismic waves in a 2D model that accounts for the pinch-out geometry related to the termination of the Holocene sedimentary layer, we can partially explain this amplification. This offshore site effect could have a crucial impact on the triggering of a submarine landslide by an earthquake in this region. More generally, this effect should be taken into account for the modeling of landslides and induced tsunamis triggered by seismic waves.

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Section: Discussionmentioning

confidence: 99%

Strong Site Effect Revealed by a New Broadband Seismometer on the Continental Shelf Offshore Nice Airport (Southeastern France)

Courboulex

Mercerat²,

Deschamps

et al. 2020

Pure Appl. Geophys.

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“…The most probable triggers of the slope failures in Swiss lakes are earthquake shaking or sediment overloading/excess pore water pressure (Stegmann et al 2007;Wiemer and Kopf 2017;Roesner et al 2019;Kremer et al 2020). Although Switzerland is a country with moderate seismicity where events with a moment magnitude M w ≥ 5.5 occur quite rarely (28 of such events have been identified for the past 700 years; Fäh et al 2016;Wiemer et al 2016;Cauzzi et al 2018), there are historical reports and prehistorical traces of earthquake-triggered tsunamis in Swiss lakes and Lake Lucerne in particular.…”

Section: Geological Settingmentioning

confidence: 99%

Geotechnical characterization and stability analysis of subaqueous slopes in Lake Lucerne (Switzerland)

et al. 2022

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Tsunamis occur not only in marine settings but also in lacustrine environments. Most of the lacustrine tsunamis are caused by seismically- or aseismically-triggered mass movements. Therefore, an assessment of the stability of subaqueous slopes is crucial for tsunami hazard assessment in a lake. We selected Lake Lucerne (Switzerland) as a natural laboratory to perform an in-depth geotechnical characterization of its subaqueous slopes. This lake experienced documented tsunamis in 1601 and 1687. Some of its slopes still bear sediment volumes with a potential for tsunamigenic failure. To identify such slopes, we interpreted available reflection seismic data and analyzed the bathymetric map. Then, we performed 152 dynamic Cone Penetration Tests with pore pressure measurement (CPTu) and retrieved 49 sediment cores at different locations in the lake. These data were used to characterize the failure-prone sediments and to evaluate the present-day static stability of subaqueous slopes. Obtained results allowed the definition of three classes of slopes in terms of static stability: unstable slopes, stable slopes close to the unstable state, and stable areas. Non-deltaic slopes with thicker unconsolidated fine-grained sediment drape and moderate-to-high slope gradients (> 5–10°) have the lowest Factor of Safety. In agreement with previous studies, the failure plane for the non-deltaic slopes is embedded within the fine-grained glaciolacustrine sediments. Deltaic slopes with prevailing coarse-grained sediments mostly appear statically stable. Finally, we generalized the measured undrained shear strength profiles $${s}_{u}(z)$$ s u ( z ) into the depth-dependent power-law models. These models define the $${s}_{u}$$ s u of Lake Lucerne’s sediments and can be applied to other lakes with similar sedimentation history.

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“…There is indeed a wide recognition that by increasing pore-fluid compressibility free gas reduces excess pore pressure build-up during earthquake loading (DeJong et al, 2014 and reference therein). Hence, despite the strong site effect revealed by Courboulex et al (2020), questions remain as to the possibility that the presence of gas mitigates the earthquake-induced liquefaction potential that Roesner et al (2019) has stressed.…”

Section: Geohazard Implicationsmentioning

confidence: 99%

Assessing Spatio‐Temporal Variability of Free Gas in Surficial Cohesive Sediments Using Tidal Pressure Fluctuations

et al. 2021

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Recognition of the widespread occurrence of gas in shallow marine sediments has sustained interest for its significance in offshore engineering activities, slope stability, and climate change (Egger et al., 2018;Fleischer et al., 2001;Kaminski et al., 2020;Sills & Wheeler, 1992). On continental shelves, methane is commonly produced by the biogenic degradation of buried organic matter (Fleisher et al., 2001;Mogollón et al., 2011). Due to the low solubility of methane in these shallow water settings, levels of dissolved gas can reach supersaturation and lead to the formation, growth, and rise of gas bubbles (Boudreau, 2012;Mogollón et al., 2011). Because temperature, pore pressure, and salinity influence biogenic reactions and determine

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Impact of seismicity on Nice slope stability—Ligurian Basin, SE France: a geotechnical revisit

Cited by 15 publications

References 59 publications

Strong Site Effect Revealed by a New Broadband Seismometer on the Continental Shelf Offshore Nice Airport (Southeastern France)

Strong Site Effect Revealed by a New Broadband Seismometer on the Continental Shelf Offshore Nice Airport (Southeastern France)

Geotechnical characterization and stability analysis of subaqueous slopes in Lake Lucerne (Switzerland)

Assessing Spatio‐Temporal Variability of Free Gas in Surficial Cohesive Sediments Using Tidal Pressure Fluctuations

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