Pop culture may have taught us that California's San Andreas Fault will one day drop the Golden State into the Pacific Ocean (it won't), but at least it has made us aware of California's looming Big One, an earthquake of magnitude 8.0 or greater. We cannot say the same for another overdue earthquake threatening the western states and Canada: the Cascadia superquake.
At least temblor-tossed Southern California features earthquake-proofed buildings and emergency-preparedness policies to handle seismic activity. Conversely, the Cascadia subduction zone — a 620-mile (1,000-kilometer) area where the Juan de Fuca plate slides under the North American plate — undergoes dormancy periods just long enough for unwary coffee-drinkers to blithely build cities elsewhere [source: Watts].
To imagine how the superquake might play out, we need only consider how a similar event affected land on the opposite side of the Ring of Fire, in Japan. In 2011 the 9.0-magnitude Tohoku quake and resultant tsunami killed 18,000 people, triggered the Fukushima meltdown and caused more than $200 billion in damages. All this happened in a region prepared for quakes, just not ones of such scale [source: Schulz].
A similar quake and tsunami has a one in 10 chance of striking the Pacific Northwest in the next half century. Under current states of awareness and readiness, such an event would shatter the Interstate 5 corridor that runs along the West Coast, killing thousands and leaving millions of refugees homeless and hungry. The chances of a smaller but still devastating quake striking in that same time frame stand at one in three [source: Schulz]. Either way, it's only a matter of time.