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TitleLong-period response spectra of large scenario earthquakes in British Columbia
AuthorMolnar, S; Ventura, C E; Finn, W D L; Cassidy, J F; Olsen, K B; Dosso, S E
SourceProceedings of the 11th Canadian Conference on Earthquake Engineering; 2015 p. 1-8
Alt SeriesEarth Sciences Sector, Contribution Series 20150045
PublisherCanadian Association of Earthquake Engineers
Meeting11th Canadian Conference on Earthquake Engineering; Victoria; CA; July 21-24, 2015
File formatpdf
ProvinceBritish Columbia
NTS104; 103; 94; 93; 82
AreaBritish Columbia
Lat/Long WENS-139.1500 -114.8667 59.9167 49.0833
Subjectsgeophysics; engineering geology; earthquakes; earthquake mechanisms; earthquake studies; plate motions; strong motion seismology; seismic risk; earthquake risk
Illustrationslocation maps; block diagrams; tables; spectra
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractNumerical simulation of large scenario earthquakes is at the forefront of seismic hazard analysis, with the potential to replace use of ground-motion prediction equations (GMPEs) in future. Three-dimensional finite-difference numerical simulation of earthquake wave propagation has been used to predict long-period (= 2 s) ground motions of potential large scenario earthquakes in British Columbia: a M9 Cascadia subduction zone mega-thrust earthquake, M6.8 deep earthquakes in the subducting oceanic plate, and M6.8 shallow earthquakes in the over-riding continental plate (Molnar et al. 2014b). New proposed ground motions for the 2015 National Building Code of Canada, up to spectral periods of 10 s, provide the opportunity to compare simulated long-period ground motions and predicted ground motions based on proposed 2015 NBCC GMPEs for the first time. This paper compares long-period response spectra estimated from 2015 NBCC GMPEs and 3D earthquake rupture simulations for potential large earthquakes in British Columbia.
Summary(Plain Language Summary, not published)
Building code provisions currently use near-surface geological conditions as a proxy for estimating variations in earthquake ground shaking. However, in areas of large sedimentary basins (such as Greater Vancouver) deep ¿basin structure¿ can play a very significant role in altering ground shaking and the resulting damage patterns from earthquakes. For example, in the 1995 M 6.9 Kobe Japan earthquake, damage was concentrated along the edge of a basin. In this study we use detailed basin models, realistic shallow earthquake scenarios, and advanced computer modelling to examine the variation in earthquake shaking across southwest BC associated with shallow earthquakes. Our study shows that sedimentary basin significantly alter the ground shaking (much more than near-surface geology currently used in building codes) with ¿deep basin¿ amplification factors of up to 8 times and much longer duration shaking (moderate shaking increasing from 3 s to 25 s duration). Studies such as this one will contribute to improving future versions of codes and standards for buildings and infrastructure.