Friday, November 02, 2012

Shaken, And Hopefully Stirred


Location of last weekend’s Earthquake - USGS


# 6691


The 7.7 quake last weekend (see Haida Gwaii Quake & Tsunami Advisories) off the northern coast of British Columbia was a not-so-gentle reminder that the Pacific Northwest is not immune to strong earthquakes.


While the San Andreas fault in Southern California is better known, the Cascadia fault that runs along the Northern California, Oregon, Washington, and B.C. coast (well south of last week’s quake) is believed capable of generating a massive earthquake/tsunami combination, much like we saw with Japan’s Great Earthquake of 2011.


Based primarily on the fact that it’s happened before.


Last year, in Just A Matter Of Time, I described how records showed that 312 years ago an orphan tsunami struck the coast of Japan, without an accompanying earth tremor being felt.


It’s origin remained a mystery for years, but today scientists - looking at sediment levels and tree growth rings – can easily see evidence of a great quake (8.7-9.2)  occurring along the Cascadia fault at that time.




Although at the time of my previous blog there was evidence of a series of major quakes along this fault line, going back thousands of years, in August of 2012 a new study was published that suggests another quake is `overdue’.


The study, was published by the USGS, and may be read at the link below:


Turbidite Event History—Methods and Implications for Holocene Paleoseismicity of the Cascadia Subduction Zone

By Chris Goldfinger, C. Hans Nelson, Ann E. Morey, Joel E. Johnson, Jason R. Patton, Eugene Karabanov, Julia Gutiérrez-Pastor, Andrew T. Eriksson, Eulàlia Gràcia, Gita Dunhill, Randolph J. Enkin, Audrey Dallimore, and Tracy Vallier



For those who would prefer not to wade through the paper, we have a press release from the Oregon State University, that explains the findings.  Excerpts follow:


13-year Cascadia study complete – and earthquake risk looms large


CORVALLIS, Ore. – A comprehensive analysis of the Cascadia Subduction Zone off the Pacific Northwest coast confirms that the region has had numerous earthquakes over the past 10,000 years, and suggests that the southern Oregon coast may be most vulnerable based on recurrence frequency.


Written by researchers at Oregon State University, and published online by the U.S. Geological Survey, the study concludes that there is a 40 percent chance of a major earthquake in the Coos Bay, Ore., region during the next 50 years. And that earthquake could approach the intensity of the Tohoku quake that devastated Japan in March of 2011.


“The southern margin of Cascadia has a much higher recurrence level for major earthquakes than the northern end and, frankly, it is overdue for a rupture,” said Chris Goldfinger, a professor in OSU’s College of Earth, Ocean, and Atmospheric Sciences and lead author of the study. “That doesn’t mean that an earthquake couldn’t strike first along the northern half, from Newport, Ore., to Vancouver Island.


“But major earthquakes tend to strike more frequently along the southern end – every 240 years or so – and it has been longer than that since it last happened,” Goldfinger added. “The probability for an earthquake on the southern part of the fault is more than double that of the northern end.”


The publication of the peer-reviewed analysis may do more than raise awareness of earthquake hazards and risks, experts say. The actuarial table and history of earthquake strength and frequency may eventually lead to an update in the state’s building codes.

(Continue . . . )



Since we can’t prevent earthquakes, and accurate prediction of when they will occur is beyond our technology, our only recourse is to prepare for them.


In January of 2011 I profiled a Washington state based preparedness educator Carol Dunn, who maintains an excellent website on the hazards faced by those living in the Pacific Northwest called 2Resilience.


You’ll find numerous resources geared for professional first responders, citizen volunteers, and families, individuals, and businesses looking to improve their level of knowledge and preparedness.



Many of us who follow @Caroldn on Twitter find her dedication and enthusiasm on preparedness issues to be quite contagious.  And if your interests lie in that direction I’d certainly recommend you include her feed.


Another resource I strongly recommend is, which promotes yearly earthquake drills and education around the country.



For more on how you can prepare for `the big one’ (even if you live someplace other than Los Angeles), I would recommend you download, read, and implement the advice provided by the The L. A. County Emergency Survival Guide.



And to become better prepared as an individual, family, business owner, or community to deal with these types of disasters: visit the following preparedness sites.






Because no matter where you live, its just a matter of time before the next disaster strikes.

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