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| Titel |
Probabilistic stability evaluation of submerged slopes in Lake Zurich (Switzerland) and seismic triggering scenarios |
| VerfasserIn |
Michael Strupler, Michael Hilbe, Flavio S. Anselmetti, Achim J. Kopf, Timo Fleischmann, Michael Strasser |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250128831
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| Publikation (Nr.) |
 EGU/EGU2016-8861.pdf |
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| Zusammenfassung |
| The consequences of subaquatic slope failures both in the marine and the lacustrine realm can
be very serious. For hazard assessments, stability analyses of submerged slopes are therefore
crucial steps, yet very complex ones, as they require knowledge of several geotechnical and
morphological factors.
Traces of subaquatic mass movements are often used to extract paleoseismological
information. For Lake Zurich, a perialpine lake in Northern Switzerland, coeval
subaquatic landslide occurrences along distinct time-correlative horizons have been
previously interpreted as earthquake-triggered. The ‘Oberrieden’ study area (∼2 km2)
shows three distinct, dated subaquatic landslides with well-defined headscarps,
translation areas and mass-transport deposits. The respective failures have been
assigned to different trigger mechanisms ranging from human-induced shore loading to
earthquake shaking. However, the local shaking intensities leading to slope failures are
unknown.
A 3.5 kHz pinger seismic reflection dataset and a 300 kHz multibeam bathymetric dataset
(1 m grid) were used for the detection of landslide features and for the layout of a coring
campaign and in situ geotechnical testing. A total of 8 Kullenberg-system piston cores (4
cores /km2) and 22 short gravity cores (11 cores /km2) were taken and 39 in situ Cone
Penetration Tests (CPT) (∼20 CPT /km2) were performed. The high density of sediment
cores and CPT sites in a well-known area allows us to include the spatial variability in the
slope model.
With a probabilistic back analysis of the earthquake-triggered ∼2210 BP subaquatic
landslide and an assessment of the actual stability of the neighbouring, unfailed sediment
drape, we analyse different scenarios of slope stability under static conditions and under
seismic shaking in order to quantitatively constrain failure mechanisms and triggers. We
apply a Monte Carlo two-dimensional limit-equilibrium infinite-slope stability model that
includes a sediment-mechanical stratigraphy constructed from a high-resolution geotechnical
dataset.The results can be used to complement the existing regional paleoseismic analysis
and give insight into possible future seismically triggered failure scenarios in the
study area. The findings from this lacustrine environment, aiming at establishing
subaquatic hazard maps, can also be transferred to applications in the marine realm. |
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