Cascadia Study Complete – Findings Show Earthquake Risks VERY Real
Over the past 13 years, researchers from Oregon State University’s College of Earth, Ocean and Atmospheric Sciences (CEOAS) have been analyzing the Cascadia Subduction Zone, a region off the Northwest coast where the Juan de Fuca tectonic plate is being subducted beneath the continent.
Chris Goldfinger, a professor at OSU’s CEOAS, is the lead author of the study, which took 4 years to complete. The 184-page report is the most comprehensive overview ever written of the Cascadia Subduction Zone. The report itself, fairly technical in nature, confirms that the region has had numerous earthquakes over the past 10,000 years. It suggests that the southern Oregon coast may be most vulnerable based on recurrence frequency. The study concludes that there is a 40 percent chance of a major earthquake in the Coos Bay, Oregon region during the next 50 years, and that the quake could approach the intensity of the Tohoku quake that devastated Japan in March of 2011.
“Over the past 10,000 years, there have been 19 earthquakes that extended along most of the margin, stretching from southern Vancouver Island to the Oregon-California border,” Goldfinger noted. “These would typically be of a magnitude from about 8.7 to 9.2—really huge earthquakes. We’ve also determined that there have been 22 additional earthquakes that involved just the southern end of the fault,” he added. “We are assuming that these are slightly smaller—more like 8.0—but not necessarily. They were still very large earthquakes that if they happened today could have a devastating impact.”
The clock is ticking on when a major earthquake will next strike, said Jay Patton, an OSU doctoral student and co-author of the study. “By the year 2060, if we have not had an earthquake, we will have exceeded 85 percent of all the known intervals of earthquake recurrence in 10,000 years,” Patton said. “The interval between earthquakes ranges from a few decades to thousands of years. But we already have exceeded about three-fourths of them.”
The last mega-earthquake to strike the Pacific Northwest occurred on January 26, 1700. Researchers know this, Goldfinger said, because written records in Japan document how an ensuing tsunami destroyed that year’s rice crop stored in warehouses.
Patrick Corcoran, a hazards outreach specialist with OSU’s Sea Grant Extension program, says West Coast residents need to align their behavior with this kind of research. “Now that we understand our vulnerability to mega-quakes and tsunamis, we need to develop a culture that is prepared at a level commensurate with the risk,” Corcoran said. “Unlike Japan, which has frequent earthquakes and thus is more culturally prepared for them, we in the Pacific Northwest have not had a mega-quake since European settlement. And since we have no culture of earthquakes, we have no culture of preparedness. The research, though, is compelling,” he added. “It clearly shows that our region has a long history of past events, and the single most important thing we can do is begin ‘expecting’ a mega-quake, then we can’t help but start preparing for it.”
For additional information regarding preparation of the Cascadia study, go to: http://oregonstate.edu/ua/ncs/archives/2012/jul/13-year-cascadia-study-complete-%E2%80%93-and-earthquake-risk-looms-large
To view the complete study, go to: http://pubs.usgs.gov/pp/pp1661f/
For more information about the OregonStateUniversity’s Collegeof Earth, Ocean and Atmospheric Sciences, visit: www.ceoas.oregonstate.edu