When the mega-thrust quake will hit
One day, the strain will be released in an instant and a catastrophic earthquake will rip down the West Coast from British Columbia to Northern California. Geologists can't predict when the mega-thrust quake will hit, but they say it is inevitable.
Parts of the coast will suddenly sink more than a metre and also shift 10 to 15 metres to the west when the tectonic plates on the 1,130-kilometre Cascadia subduction zone slide past each other.
The ground shaking will be so intense older bridges and unreinforced buildings will crack and many are expected to collapse. Landslides will cut off roads, railways and millions of people could be left - for days, and in some areas, possibly weeks - without phone, cable, power and water. The coast will be hammered as a tsunami sends a wall of water racing ashore that could wash away resorts, campgrounds, rearrange shipping channels and sever major undersea cables.
"There would be widespread damage, including thousands of injuries and fatalities and the destruction of hundreds of buildings," says a recent report from B.C.'s auditor general that harshly criticized the province for not being better prepared for the catastrophe and its aftershocks.
Megaquakes on North America's west coast are rare, but occur like clockwork about every 500 years, say scientists, who have uncovered evidence of 19 giant Cascadia quakes over the last 10,000 years.