July 1, 2014 | Portland Monthly--Think of Oregon geology as a clock, measuring time in earthquakes—40 major coastal quakes over the last 10,000 years. Tick: a magnitude 8 on the Richter scale. (Bigger than the quake that killed 63 people in the Bay Area in 1989.) Tock: a magnitude 9. (Same as the 2011 quake that killed almost 16,000 in Japan.) On average, a major quake uncorks in this area every 243 years, the last one on January 26, 1700—314 years ago.
Right. We’re overdue.
When the next Big One does happen, a 700-mile chunk of tectonic plate known as the Juan de Fuca, stretching from British Columbia to Northern California, will slide beneath the North American plate, causing the entire Northwest coastline to sink by up to 6.6 feet. The resulting quake won’t be a California-style short blast of energy along a fault line in the earth’s upper crustal zone. It will be bigger, deeper, and longer: 3–4 minutes, with potentially dozens of aftershocks, some very powerful, for days, even months, later. READ FULL ARTICLE