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TitleDoes the microtremor array method provide reliable vs profiles in comparison with commercial techniques?
AuthorMolnar, S; Dosso, S E; Cassidy, J FORCID logo
SourceEos, Transactions of the American Geophysical Union vol. 90, no. 22, 2009, 1 pages
Alt SeriesEarth Sciences Sector, Contribution Series 20080720
MeetingAmerican Geophysical Union/Canadian Geophysical Union Joint Meeting; Toronto, ON; CA; May 2009
Mediapaper; on-line; digital
Subjectsgeophysics; engineering geology; earthquakes; earthquake studies; earthquake mechanisms; seismicity; surface wave studies; seismic waves
ProgramReducing Risk from Natural Hazards
Released2009 01 01
AbstractEarthquake engineering practice is based significantly on the shear-wave velocity of subsurface sediments and rock. Our research examines the relatively-new microtremor array method of estimating shear-wave velocity profiles at two urban centers in SW British Columbia that represent very different geological environments, and compare the results to traditional methods. The microtremor array method is based on recording background seismic noise using a spatial array of several seismographs to extract the associated surface wave dispersion that is used to invert for the shear-wave velocity profile of the site. The method has become increasingly popular worldwide because it makes use of continuously-available and wide-band (0.02-50 Hz) seismic noise, requires little equipment, and is unobtrusive to the site, resulting in relatively fast, easy, and low-cost measurements. We performed microtremor array measurements in the cities of Victoria and Vancouver, which represent end member geological conditions. The local geology of Victoria generally exhibits a strong near-surface impedance contrast (< 30 m of soft marine silts over very stiff bedrock), in contrast to Vancouver where impedance contrasts are much deeper and weaker (up to 500 m of over-consolidated glacial material and up to 500 m of deltaic sands and silts from the Fraser river, resulting in a maximum of 1 km of material over bedrock). The wide frequency band of the noise wavefield (due primarily to ocean waves at < 0.5 Hz and anthropogenic sources at > 1 Hz) is found to adequately characterize the subsurface, even in Vancouver. The shear-wave velocity profiles obtained at each site using various array configurations and dispersion analysis procedures are compared with shear-wave measurements from three different commercial techniques; seismic cone penetration testing, surface refraction, and surface-to-downhole.

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