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TitleRevisiting earthquake site response in Vancouver, Canada
AuthorMolnar, S; Cassidy, J F; Jackson, F; Brillon, C
SourceSeismological Society of America, Proceedings vol. 87, no. 2B, 2016 p. 494
LinksDownload entire publication / téléchargement de la publication au complet (21.7 MB)
Alt SeriesEarth Sciences Sector, Contribution Series 20160055
PublisherSeismological Society of America
MeetingSeismological Society of America Annual Meeting; Reno, NV; US; April 20-22, 2016
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
Subjectstectonics; earthquake magnitudes; earthquakes; earthquake studies; array seismology
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractOn December 30, 2015 a M 4.7 earthquake occurred within the subducting Juan de Fuca plate about 40-80 km south of greater Vancouver, British Columbia, Canada. This produced the strongest shaking in the region since the 2001 M6.8 Nisqually, Washington State, earthquake, and the first to occur since a dense strong-motion network was deployed in southwestern British Columbia. In this study, we focus on the ground shaking variation in British Columbia on a wide variety of soil conditions, from bedrock, to firm soil, to the thick (up to 600 m) unconsolidated Holocene sediments of the Fraser River delta. On bedrock, peak ground acceleration values of about 0.4% g were recorded, whereas soil sites showed peak ground accelerations up to 5% g. In this study we document site response using; single-station HV spectral ratios at each of the strong-motion recording sites, spectral ratios using nearby bedrock reference recordings; and reported felt intensities and compare with the results of previous studies using recordings of moderate earthquakes. As in previous earthquakes, the strongest observed shaking was observed near the northern part of the Fraser River delta, suggesting that basin edge effects and/or resonance effects are important.
Summary(Plain Language Summary, not published)
This study examines earthquake site response across greater Vancouver using recordings of a widely-felt magnitude 4.7 earthquake. This is the first significant earthquake recorded on our dense strong motion network in the Vancouver area that was deployed to examine variations in earthquake shaking on a wide variety of soil conditions (from rock, to firm soil, to thin soft soil, to thick soft soil). Some of Canada's most important infrastructure (e.g., ports, airports) is located here. We also compare our site response results to several thousand felt shaking intensities reported across the region. This will help us to better constrain earthquake shaking during future earthquakes and to improve our national building codes and standards.