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TitleShear wave measurements for earthquake response evaluation in Orleans, Ontario
AuthorCrow, H; Pyne, M; Hunter, J A; Pullan, S E; Motazedian, D; Pugin, A
SourceGeological Survey of Canada, Open File 5579, 2007, 26 pages; 1 CD-ROM,
Documentopen file
MediaCD-ROM; digital; on-line
File formatreadme
File formatdat; pdf (Adobe® Acrobat® Reader® v.5.0 +); txt; zip
NTS31G/05NE; 31G/06NW; 31G/11SW; 31G/12SE
AreaOrleans; Ottawa
Lat/Long WENS -75.6000 -75.4333 45.5167 45.4167
Subjectsgeophysics; surficial geology/geomorphology; engineering geology; seismology; earthquakes; geophysical logging; boreholes; seismic methods; seismic energy; seismic refraction surveys; seismic reflection surveys; seismic profiles; seismic waves; s waves; seismic velocities; travel-time analyses; soil mechanics; sediment properties; sediment distribution; postglacial deposits; marine sediments; soils; clays; sands; silts; stratigraphic analyses; overburden thickness; bedrock topography; buried valleys; building codes; Holocene; Pleistocene; slope stability; slope failures; landslides; Champlain Sea Sediments; geological hazards; seismic hazard; risk assessment; site response; ground shaking; shear waves; amplification; Phanerozoic; Cenozoic; Quaternary
Illustrationstables; sketch maps; digital elevation models; schematic representations; photographs; geophysical images; plots; profiles; forms
Natural Resources Canada Library - Ottawa (Earth Sciences)
Natural Resources Canada library - Québec (Earth Sciences)
Geological Survey of Canada (Atlantic)
Natural Resources Canada library - Calgary (Earth Sciences)
Natural Resources Canada library - Vancouver (Earth Sciences)
ProgramReducing Risk from Natural Hazards
Released2007 06 01
AbstractThe Geological Survey of Canada and Carleton University collected shear wave data at 63 seismic sites in the Ottawa suburb of Orleans as part of the Eastern Canada Geohazards Assessment Project. Data collection techniques included reflection/refraction and landstreamer profiling. Previous collection and analysis of high-resolution borehole velocity logs in 18 borings in the Ottawa-Montreal area led to the definition of an average shear-wave velocity-depth function unique to these sediments. This formula, when applied to 835 borehole logs from within Orleans, was used to estimate a Vs30 value at each location, based on the soil type described in the log. The combined data from surface seismic sites and derived velocity-depth calculations were contoured to produce a Vs30 map of Orleans. Shear wave velocity and post-glacial thickness information was also used to produce a fundamental site period map.
High Vs30 values (>1500 m/s) were calculated in areas of thin overburden, and very low Vs30 values (<180 m/s) were obtained in areas underlain by thick deposits of post-glacial sediments. Of note is a buried bedrock valley with steep sides which extends in an elongate, NE-SW trend for approximately 2.5 km under Orleans. Borehole data alone did not clearly define the extent or depth of the clay-filled bedrock valley, which reached a depth of 95 meters in places. Due to the high velocity contrast between post-glacial sediments and bedrock in the Ottawa area, ongoing research is being carried out to address the unusually high soil amplification factors observed in the study area.