CGRG Bibliography of Canadian Geomorphology
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Author : Bobrowsky, P.T.
Date : 2001.
Title : Tsunamis and ground subsidence on Canada's west coast.
Publication : St. John's 2001. Geological Association of Canada - Mineralogical Association of Canada 2001 Joint Annual Meeting / l'Association géologique du Canada - l'Association minéralogique du Canada réunion annuelle conjointe. Memorial University, St. John's, Newfoundland, May 27-30 2001.
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Abstract
Throughout the Holocene, the coast of British Columbia has been affected repeatedly by both tsunamis and ground subsidence generated by either local or distant earthquakes. Historical data in the province indicate that earthquakes occurring beyond Canada’s west coast can generate tsunamis that can seriously impact British Columbia’s coastal zone. For example, the 1964 great (Mw 9.2) Alaska earthquake generated a tsunami that had local run-up heights approaching 5 meters in the Port Alberni area, with subsequent resulting damage exceeding $10 million (Canadian 1964 dollars). Moreover, the geological record provides further evidence for a repeated cycle of tsunamis (locally and extra-locally generated) and ground subsidence (locally generated) that impacted the coast during the last few thousand years. Calculated subsidence is estimated to be about 1 meter. The most widely preserved subsidence event is the AD 1700 great Cascadia subduction zone earthquake. Sonic drill core from intertidal marsh areas near Port Alberni contains evidence for up to 8 tsunami events spanning the last 4000 years. The implications of the historic and prehistoric evidence, coupled with sophisticated numerical modeling data, suggests that the west coast of Canada will be significantly affected by one or both of these types of events in the not to distant future. Subsidence on the order of ca. 1 meter and tsunami run-up heights of up to 20 meters is expected in certain areas of the province and this provides a serious threat to people in the region. Unlike scenarios during previous events, the next prominent tsunami or ground subsidence event will now affect a substantial population base within the province as more people naturally migrate to the coastal zone. Depending on the scale of the disaster, the economic costs and the affect on the provincial infrastructure will likely be prohibitive.
Bibliography of Canadian Geomorphology