Chapter 21: Near-surface Shear-wave Velocity Measurements for Soft-soil Earthquake-hazard Assessment: Some Canadian Mapping Examples
J. A. Hunter, D. Motazedian, H. L. Crow, G. R. Brooks, R. D. Miller, A. J.-M. Pugin, S. E. Pullan, J. Xia, 2010. "Near-surface Shear-wave Velocity Measurements for Soft-soil Earthquake-hazard Assessment: Some Canadian Mapping Examples", Advances in Near-surface Seismology and Ground-penetrating Radar, Richard D. Miller, John H. Bradford, Klaus Holliger
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The shear-wave velocity profile of a near-surface soil and/or rock site is one of the most important parameters for geotechnical estimation of earthquake shaking response at the ground surface. Downhole and surface seismic methods for measuring shear-wave velocities and mapping subsurface impedance boundaries include seismic cone penetrometer, downhole shear-wave vertical seismic profiling, surface-geophone array sites using refraction and reflection methods including array-to-source reversals, multichannel analysis of surface waves, seismic-reflection profiling, and horizontal-to-vertical spectral analyses of ambient noise. A suite of seismic shear-wave measurement methods has been tested in two Canadian cities with relatively high seismic hazard. Regional maps of National Earthquake Hazard Reductions Program (NEHRP) seismic site classifications (following the National Building Code of Canada) and fundamental site periods were created with the data. These maps indicate that broadband amplification effects and fundamental resonance periods can be extremely variable over short lateral distances within both survey areas. Such information needs to be considered by land-use planners and engineers working in such areas. Shear-wave velocity techniques constitute the most versatile approaches to earthquake-hazard mapping and site investigations.
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Near-surface seismology and ground-penetrating radar (GPR) have enjoyed success and increasing popularity among a wide range of geophysicists, engineers, and hydrologists since their emergence in the latter half of the twentieth century. With the common ground shared by near-surface seismology and GPR, their significant upside potential, and rapid developments in the methods, a book bringing together the most current trends in research and applications of both is fitting and timely. Conceptually, near-surface seismology and GPR are remarkably similar, and they share a range of attributes and compatibilities that provides opportunities to integrate processing and interpretation workflows, which makes them a perfect pair to share pages in a book.
With growth in numbers and professional emphasis have come sections, focus groups, and even professional societies specifically promoting near-surface geophysics. The emergence of near-surface geophysics groups, beginning in the late 1990s and extending into the early twenty-first century, has fueled a diversity of opportunities for professional collaborations. A range of workshops and shared publications has been the fruit of collaborative efforts. The near-surface community continues to extend and develop methods and approaches necessary to satisfy increasing demands in some of the socioeconomically pertinent disciplines such as civil and environmental engineering and hydrology. This book represents the first formal cooperative effort undertaken by the near-surface communities of the Society of Exploration Geophysicists, the American Geophysical Union, and the Environmental and Engineering Geophysical Society.