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TitleIn situ damping measurements in Leda Clay within the Ottawa, ON area
AuthorCrow, H; Hunter, J A; Pugin, A J -M; Motazedian, D
SourceGeo2010, proceedings of the 63rd Annual Canadian Geotechnical Conference and the 6th Canadian Permafrost Conference; 2010, 9 pages
Year2010
Alt SeriesEarth Sciences Sector, Contribution Series 20100088
Meeting63rd Canadian Geotechnical Conference and the 6th Canadian Permafrost Conference; Calgary; CA; September 12-16, 2010
Documentbook
Lang.English
Mediapaper
RelatedThis publication is contained in Wang, X; Zhang, Y; Fraser, R; Chen, W; (2010). Evaluating the major controls on permafrost distribution in Ivvavik National Park based on process-based modelling; Evaluating the major controls on permafrost distribution in Ivvavik National Park based on process-based modelling; Evaluating the major controls on permafrost distribution in Ivvavik National Park based on process-based modelling; Evaluating the major controls on permafrost distribution in Ivvavik National Park based on process-based modelling, Geo2010, proceedings of the 63rd Annual Canadian Geotechnical Conference and the 6th Canadian Permafrost Conference
ProvinceOntario
NTS31G/05
AreaOttawa
Lat/Long WENS -76.0000 -75.5000 45.5000 45.2500
Subjectssurficial geology/geomorphology; geophysics; sedimentary rocks; clays; seismic risk; seismicity; earthquakes; seismic interpretations; seismic surveys; reflection studies; seismic reflection surveys
Illustrationsseismic profiles; plots
ProgramEastern Canada Geohazards Assessment Project, Public Safety Geoscience
AbstractIn the Ottawa area, unusually high amplification ratios have been recently measured in Leda Clays at low levels of earthquake-induced ground shaking. However, the contribution of seismic Q, or material damping (sin=1/2Q), on the overall ground motion at soft soil sites across the city is not well understood. This research is contributing attenuation measurements in soft soils (Vs<250m/s) for ongoing seismic hazard evaluation in the Ottawa area. The work focuses on in situ measurements of damping in two deep boreholes drilled into Leda Clay. A new approach to the spectral ratio technique is developed for the measurement of Q in the field using a mono-frequency vibratory source, and two identical downhole 3-component geophones. Analysis of the data yield small strain Q's ranging from 40 (Damping 1.2%) to greater than 140 (or damping of ~0.4%), and stratigraphy is found to be a significant factor controlling the in situ soil
response.
GEOSCAN ID285593