Over the past 10,000 years, 22 major earthquakes have struck the southern part of the Cascadia fault, which runs off the Oregon coast from Coos Bay to Newport. And apparently, Mother Nature may be ready to strike Oregon again. After analyzing 13 years of research, scientists at Oregon State University have announced that this region has a 40 percent chance of suffering a massive earthquake in the next 50 years. And if Oregon is rocked by a temblor, researchers suggest that it could even be the same magnitude as the tremor that devastated Japan last year. Scientists have long warned that Oregon needs to upgrade its infrastructure to prepare for such an event, but so far, not much has been done. Here's what you should know:
How did researchers make this prediction?
OSU scientists studied the historic intervals between earthquakes over the last 10,000 years in the Cascadia Subduction Zone — a 680-mile fault off the coast of Oregon. Earthquakes aren't so predictable that they happen like clockwork every X number of years, but scientists can still make informed guesses based on the frequency with which earthquakes have occurred in the past. And because the last major earthquake in the area occurred all the way back in 1700, a major temblor in the next 50 years is almost more likely than not. "If the Cascadia fault had a warranty against failure," says lead author Chris Goldfinger, "it would have expired many years ago."
Would it be as bad as Japan's 2011 quake?
Maybe. Scientists peg the chance of a Japan-level 9.0 quake at 10 percent. A tremor that size would reverberate across the entire Oregon coast. Meanwhile, the southern Oregon coast and part of the northern California coast — from Florence, Ore., down to Cape Mendocino, Calif. — has a 40 percent chance of an earthquake with a magnitude between 8.1 and 8.3. That's not as powerful as Japan's tsunami-triggering quake — but it still could be devastating. By comparison, the deadly earthquake that crippled San Francisco in 1989 measured 7.1.
Is Oregon prepared for such an event?
Not really. The threat to the state is not just the strength of a possible earthquake, but also the length of time it lasts. A tremor at the Cascadia Subduction Zone would probably last three to five minutes, says Scott Ashford, a professor at OSU not involved with the study, but many buildings are only meant to withstand quakes that last about 30 seconds. "Oregon is not ready," Ashford tells The Oregonian. "We have a bunch of legacy infrastructure, but it's never been tested and was never designed for Cascadia Subduction Zone earthquakes."
How bad would the devastation be?
Pretty bad. Perhaps the biggest problem for Oregon would be liquefaction, a process in which wet, loose soil behaves like liquid. Yumei Wang of the Oregon Department of Geology and Mineral Industries says that the state's riverbank port terminals are all on easily liquefied soil, which means that buried tanks and pipes could float out of the ground, and buildings could sink. Roads would become impassable, electricity would be out, and lives would be at severe risk. In other words, Oregon needs to prepare. Patrick Corcoran, a hazards outreach specialist at OSU, tells ScienceBlog: "The single most important thing we can do is begin 'expecting' a mega-quake, then we can't help but start preparing for it."
Sources: AFP, Government Security News, The Oregonian, ScienceBlog, USGS