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TitleFailure mechanism of an ancient landslide at Low, Quebec
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorWang, B
SourceGeological Survey of Canada, Open File 8539, 2019, 19 pages, Open Access logo Open Access
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
File formatpdf
Lat/Long WENS -76.0000 -75.5000 46.0000 45.7500
Subjectssurficial geology/geomorphology; engineering geology; geophysics; Holocene; landslides; landslide deposits; marine sediments; marine clays; sensitive clays; soils; earthquakes; earthquake magnitudes; geophysical surveys; seismic surveys, ground; overburden thickness; shear tests; penetrometers; shear strength; slope stability; slope stability analyses; slope failures; modelling; seismographs; grain size distribution; plasticity; liquid limit analyses; pore pressures; pore fluids; geological history; depositional history; tectonic history; Low Landslide; Champlain Sea Clay; South Nation River Landslide; Lemieux Landslide; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; geophysical images; tables; graphs; profiles; cross-sections; models
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2019 02 06
AbstractThis Open File presents a geotechnical study of a Champlain Sea clay landslide near the municipality of Low, Quebec. The landslide is one of 12 landslides identified from previous studies to have been triggered by an earthquake about 1020 cal yr BP. Geotechnical studies were conducted to investigate the failure mechanism of the landslide. This is one of three landslides investigated for the purpose of estimating the minimum magnitude of the earthquake. Field tests were conducted in and around the landslide zone. Micro-seismic surveys at 27 locations indicate the sediment thickness ranging from 10 m to 44 m below the current surface. Cone Penetrometer Tests (CPT) at four locations confirmed the micro-seismic measurements to be fairly accurate. The CPT tip resistance data were calibrated with field Vane Shear Test (VST) results. The soil peak undrained shear strength (Cu) is found to correlate with depth (H) from the original Champlain Sea surface as Cu = 28 + 1.42H. The test results and other information indicate that the 1020 cal yr BP landslide likely occurred inside a larger landslide zone of a much older age. The landslide is likely a flake type failure based on the data collected and by comparison with other cases. A slope model is constructed for stability analysis to determine the threshold ground acceleration required to trigger the failure. The resulting minimum horizontal ground acceleration is 0.19 g.
Summary(Plain Language Summary, not published)
This Open File documents detailed geotechnical studies of an ancient landslide near Low, Quebec. The landslide is one of three landslides investigated in the general Ottawa-Gatineau region. The landslides were triggered by an earthquake about a thousand years ago. The purpose of the study is to estimate the minimum ground shaking required to trigger the landslides. The information is then used to calculate the minimum magnitude of the earthquake. The ultimate objective is to understand the prehistoric seismicity of the region. Details of the other two landslide studies have been reported separately. This Open File presents the results from the Low site. Field testing allowed reconstruction of the slope for stability analysis. The analysis indicates a minimum ground acceleration of 0.19 g required to trigger the Low landslide. The result is consistent with other observations in the region.

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