Vancouver and the densely populated Lower Mainland region of southwest British Columbia are situated over an active subduction zone. The dynamic geological setting makes this region subject to frequent seismic activity and contributes to a higher risk of large
damaging earthquakes than in other parts of Canada. Earthquakes that may present a hazard to the area occur in three distinct source regions: earthquakes within the continental crust, deeper earthquakes within the subducted oceanic plate, and earthquakes on the subduction boundary between the
lithospheric plates. While Vancouver (incorporated in 1886) has not experienced a damaging earthquake in its short history, large earthquakes nearby have been strongly felt and there is paleoseismic evidence for very strong shaking in prehistoric time. Most of the region is placed in Seismic Zone 4
in the 1995 edition of the National Building Code of Canada. Ongoing microearthquake activity, and earthquakes strong enough to be felt occurring in most years, are reminders of the seismic hazard.
In March, 2007, 305.9 km2 of Light Detection and Ranging (LIDAR) observations and digital aerial imagery were acquired on southern Vancouver Island, British Columbia, for earthquake and tsunami investigations by Natural Resources Canada. The imagery covers the
Leech River Fault Zone and coastal regions from Sombrio Point to Ten Mile Point. The geographic extent ranges from 48.3 to 48.5°N and from 123.2 to 124.3°W. A 2 m x 2 m bare-Earth digital elevation model (DEM) was derived from the LIDAR observations and is complemented by 0.2 m x 0.2 m
pixel width colour aerial imagery collected at the same time.
Strong ground-motion recordings of the magnitude (MW) = 5.3 1976 Pender Island, British Columbia and MW = 5.1 1996 Duvall, Washington earthquakes provide the best constraints, to date, on seismic site response on the Fraser delta. At low frequencies, seismic
amplification occurs on the thick soils of the Fraser delta relative to rock and firm-soil sites. The amplification is more pronounced in the horizontal component of ground motion than in the vertical. At high frequencies, modest attenuation is observed on the thick soils. The crossover from
amplification to attenuation occurs in the 5-8 Hz bandwidth. The largest ground accelerations recorded were not on the thickest sediments, but nearer the edge of the delta where the deltaic sediments and underlying Pleistocene sediments are thinner. This represents a hazard that should be taken into
account when siting buildings near the delta edge.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.