Geoscientists working on the west coast of North America from northern California to southwestern British Columbia have demonstrated that giant (magnitude-9) earthquakes occur along the Cascadia subduction zone, where the oceanic Juan de Fuca plate moves down beneath the edge of North America. The geologic evidence includes sudden land-level change, tsunami deposits, and sediments generated by liquefaction, and submarine landslide deposits (‘turbidites’) on the Pacific Ocean floor.
The turbidite record spans the past 10,000 years and provides evidence for 20 giant earthquakes with an average return period of 500 years. The most recent of these earthquakes happened in January 1700. Satellite global positioning data extending back to the mid-1990s shows a pattern of land-surface deformation consistent with locking of the fault separating the Juan de Fuca and North America plates, marking the build-up to the next giant earthquake. Although the next of these earthquakes will damage all cities from Portland to Vancouver, the risk profile of far more frequent, magnitude 6 and 7 crustal earthquakes is greater than that of much larger, but rarer plate-boundary events.
This presentation will discuss the likely effects on Metro Vancouver of very rare, plate-boundary earthquakes and more common, magnitude 6–7 earthquakes. The assessment is based on recent research that has identified active faults in the Pacific Northwest and the damage caused by similar earthquakes, notably those in Sumatra in 2004, Japan in 2011, and Christchurch in 2011. John will also discuss strategies for reducing both the primary and secondary damage of future earthquakes.
John Clague is Emeritus Professor at Simon Fraser University. He was educated at Occidental College (BA), the University of California Berkeley (MA), and the University of British Columbia (PhD). Clague worked as a Research Scientist with the Geological Survey of Canada from 1975 until 1998. In 1998 he accepted a faculty position in Department of Earth Sciences at Simon Fraser University. He is currently Director of the Centre for Natural Hazard Research at SFU. Clague is a Fellow of the Royal Society of Canada, former President of the Geological Association of Canada, and Past-President of the International Union for Quaternary Research and Engineers and Geoscientists BC. He is recipient of the Geological Society of America Burwell Award, the Royal Society of Canada Bancroft Award, Engineers and Geoscientists BC’s Innovation Editorial Board Award, the Geological Association of Canada’s (GAC) E.R.W Neale Medal, and GAC’s Logan Medal and Ambrose Medal. He was the 2007–2008 Richard Jahns Distinguished Lecturer for the Geological Society of America and Association of Environmental and Engineering Geology and received an Honorary PhD from the University of Waterloo in 2017.
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