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

Abstract

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.

Submarine landslide tsunami hazard assessment for the Western Makran based on a deterministic approach

“…However, we already know that such voluminous submarine landslides generally do not occur on such steep slopes as the thick layer of unconsolidated failure-prone sediments does not usually accumulate on slopes steeper than 15° (Masson et al, 2006a). To avoid this kind of overestimate, geological, sedimentological, and geotechnical studies and field work are needed to for finding the potential submarine landslide locations and defining the worst-case scenarios (Shynkarenko et al, 2022). In this article, due to the huge gap between maximum and average wave height, we can conclude that assuming wave heights as huge as 5.5m can be considered an overestimation for Chabahar.…”

Towards a Dynamic Earthquake Risk Framework for Switzerland

“…Geographic features, such as large and deep peri-alpine lakes, steep slopes, and alluvial basins with a high-water 114 table, make Switzerland susceptible to secondary hazards (e.g., Fritsche et al, 2012;Fäh et al, 2012). Using 115 geophysical imaging, seismic monitoring, numerical modelling and other techniques, the SED has been 116 conducting research on earthquake-induced hazards, including (i) rockfalls and landslides (e.g., Burjanek et al, 117 2018;Kleinbrod et al, 2018;Glueer et al, 2021;Häusler et al, 2022); (ii) lake tsunamis (e.g., Strupler et al, 118 2018;Kremer et al, 2022;Shynkarenko et al, 2022); and (iii) liquefaction (e.g., Fritsche et al, 2012;Roten et 119 al., 2014;Janusz et al, 2022). Findings from these studies have been incorporated into rapid estimates of 120 earthquake-induced mass movements and liquefaction probabilities in Switzerland via the SED ShakeMap 121 application (Cauzzi et al, 2018a;Section 3.3).…”