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July 11, 2011 / Dave Gorham

DHS Considers Devastating West Coast Tsunami "When, Not If"

We’re all familiar with the Department of Homeland Security. Created in 2002 following the September 11th terrorist attacks, the DHS is a cabinet department of the United States federal government with the primary responsibility of protecting the United States from, and responding to terrorist attacks. Additionally, and perhaps not as well known, it plans for and responds to man-made emergencies and natural disasters. Its mission: To strengthen America’s security and resiliency by providing knowledge products and innovative technology solutions for the Homeland Security Enterprise (HSE).

But did you know DHS’ Science and Technology division is presently working with experts in the fields of earthquake and tsunami prediction to help local and state-level governments better prepare for what many believe will be one of the world’s most powerful earthquakes and the likelihood of the devastating tsunami “the Big One” will generate? Should the Big One occur, estimates of damage along the U.S. West Coast from a tsunami could easily run into the many billions of dollars, with massive and widespread devastation that will spread far inland.

This massive quake is expected along the Cascadia Subduction Zone just 75 miles off the coast of northern California, Oregon, Washington and southern Canada, where the Pacific Plate is subducting underneath the North American Plate. The Cascadia can produce very large earthquakes of magnitude 9.0 and greater. Some fear it is capable of producing an as-yet unrecorded 10.0 magnitude. In fact, over the past 3,500 years seven major Cascadia earthquakes have occurred with some regularity, suggesting a return rate of 300-600 years; the last significant earthquake happened in January of 1700 — 311 years ago.

The Cascadia Subduction Zone. Image: Wikipedia

The expected future Cascadia quake is the worst case scenario model that DHS must prepare for. Even though scientists predict only a 14% chance of the Cascadia quake striking the Pacific Northwest within the next 50 years, it’s a number too large to ignore. Should this scenario unfold as suggested, reaction times to the resulting tsunami will be measured in minutes, not hours. Remember, the tsunami generated by the Tohoku Earthquake in March took only six hours to cover the 2,500 miles from the epicenter near the northeast coast of Japan to the coast of Alaska, at a rate of more than 400mph. Consider too: this “far away” earthquake did more than $30 million dollars in damage to Hawaii, $7 million dollars in damage to coastal Oregon and more than $50 million dollars in damage to the northern coast of California. Despite the seemingly low 14% chance for the 9.0 magnitude or greater Cascadia quake, most experts agree that it’s “when,” not “if” and “sooner” rather than “later.”

Cascadia Subduction: The world's smallest tectonic plate, the Juan de Fuca, is a divergent boundary of the Pacific Plate (the world's largest tectonic plate), that is sliding underneath the North American Plate. Experts believe the building stress between the two (possibly three) plates will release an earthquake that may be the most powerful ever recorded. Image: Wikipedia

It was only last year that an 8.8 magnitude earthquake off the coast of Chile (YourWeatherBlog) destroyed the fishing industry for many regions of Chile’s coastline. In 2009, a powerful earthquake south of Samoa triggered a tsunami that claimed more than 200 lives. And in 2004, more than 200,000 lives were lost when a massive 9.0 quake off the coast Sumatra struck coastlines of the Indian Ocean and Bay of Bengal.

One of the reasons the damage is expected to be so high is the lack of warning. It’s possible that, depending on the exact location of the quake, the tsunami will take only 10 minutes to reach the coast of California leaving precious little time to react after the sirens alert coastal populations. Knowing which areas are most at risk, what to do, where to go and when to act are key elements in tsunami defense. Therefore, public education remains high on the list of actions by Homeland Security.

For tsunami alerts and warnings to be effective, systems must work perfectly, communicate with each other and be multi-layered. Post-analysis reports following the 9/11 terrorist attacks revealed many levels of communication that were severely handicapped (some deemed completely ineffective) due to their inability to communicate across platforms and various agencies of police, fire, government, rescue and more. West Coast officials look to New York and know that multi-layered one- and two-way communications consisting of cell, phone, voice, reverse 911, text, fax, email, public address, radio and television — even amateur radio — are integral to the success of a tsunami or natural disaster alerting plan. However emergency plans are only as good as the actions taken by the individuals who use them, which is why DHS is analyzing a wide range of disaster scenarios, while examining the latest technology in communications and the science of earthquake and tsunami prediction and creating and enhancing programs to increase public awareness.

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