A subaqueous hazard map for earthquake-triggered landslides in Lake Zurich,Switzerland |
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Authors: | M Strupler L Danciu M Hilbe K Kremer F S Anselmetti M Strasser S Wiemer |
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Institution: | 1.Geological Institute, ETH Zurich,Zurich,Switzerland;2.Swiss Seismological Service,ETH Zurich,Zurich,Switzerland;3.Institute of Geological Sciences and Oeschger Centre for Climate Change Research,University of Bern,Bern,Switzerland;4.Institute of Geology,University of Innsbruck,Innsbruck,Austria |
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Abstract: | The awareness of geohazards in the subaqueous environment has steadily increased in the past years and there is an increased need to assess these hazards in a quantitative sense. Prime examples are subaqueous landslides, which can be triggered by a number of processes including earthquakes or human activities, and which may impact offshore and onshore infrastructure and communities. In the literature, a plenitude of subaqueous landslide events are related to historical earthquakes, including cases from lakes in Switzerland. Here, we present an approach for a basin-wide earthquake-triggered subaquatic landslide hazard assessment for Lake Zurich, which is surrounded by a densely populated shoreline. Our analysis is based on high-resolution sediment-mechanical and geophysical input data. Slope stabilities are calculated with a grid-based limit equilibrium model on an infinite slope, which uses Monte Carlo sampled input data from a sediment-mechanical stratigraphy of the lateral slopes. Combined with probabilistic ground-shaking forecasts from a recent national seismic hazard analysis, subaquatic earthquake-triggered landslide hazard maps are constructed for different mean return periods, ranging from 475 to 9975 years. Our results provide a first quantitative landslide hazard estimation for the lateral slopes in Lake Zurich. Furthermore, a back-analysis of a case-study site indicates that pseudostatic accelerations in the range between 0.04 and 0.08 g were needed to trigger a well-investigated subaqueous landslide, dated to ~2210 cal. years B.P. |
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