CGRG Bibliography of Canadian Geomorphology
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Author : Harris, J.B.; Hunter, J.A.; Aylsworth, J.M.; Burns, R.A.; and Good, R.L.
Date : 2005.
Title : Downhole measurement of shear-wave splitting in Holocene sediments: application to landslide hazards in the Ottawa Valley, Canada.
Publication : Eos Transactions. American Geophysical Union Joint Assembly Supplement, Spring Meeting, 23–27 May 2005, New Orleans, Louisiana, USA.
Issue : 86(18):
Page(s) : #NS14A-03.
Abstract
Stress-aligned inclusions (pore spaces and microfractures) cause seismic shear waves to exhibit directional polarizations in response to propagation through azimuthally anisotropic sediments. This phenomenon, called shear-wave splitting, is observable by measuring differences in shear-wave velocity between waves traveling parallel (S1 - fast shear wave) and perpendicular (S2 - slow shear wave) to the trend of the inclusions. This investigation provides evidence of shear-wave splitting in Holocene sediments of the Ottawa Valley (southern Ontario), Canada. Preliminary analysis of a multicomponent downhole data set, recorded using hammer and mass energy sources, indicates shear-wave splitting related to in-situ stresses associated with steep, landslide-prone, slopes bounding the South Nation River. Orientation of the split shear waves, determined from particle motion plots of the three-component downhole records, shows alignment of the polarization directions with the local topography and analysis of travel-time delays between S1 and S2 suggests anisotropy values of approximately 7% for the upper 30 m of the subsurface. Temporal monitoring of changes in shear-wave splitting may provide a method to evaluate factors related to landsliding, and assist in identifying potentially unstable slopes
Bibliography of Canadian Geomorphology