The major earthquakes that devastated Chile earlier this year and which triggered the catastrophic Indonesian tsunami of 2004 are more than just a distinct possibility to strike the Pacific Northwest coast of the United States, scientists say.
There is more than a one-in-three chance that it will happen within the next 50 years.
New analyses by Oregon State University marine geologist Chris Goldfinger and his colleagues have provided fresh insights into the Northwest’s turbulent seismic history – where magnitude 8.2 (or higher) earthquakes have occurred 41 times during the past 10,000 years. Those earthquakes were thought to generally occur every 500 years, but as scientists delve more deeply into the offshore sediments and other evidence, they have discovered a great deal more complexity to the Cascadia Subduction Zone.
“What we’ve found is that Cascadia isn’t one big subduction zone when it comes to major earthquakes,” Goldfinger said. “It actually has several segments – at least four – and the earthquake activity is different depending on where a quake originates. The largest earthquakes occur in the north and usually rupture the entire fault. These are quakes of about magnitude-9 and they are just huge – but they don’t happen as frequently.
“At the southern end of the fault, the earthquakes tend to be a bit smaller, but more frequent,” he added. “These are still magnitude-8 or greater events, which is similar to what took place in Chile, so the potential for damage is quite real.”
Based on historical averages, Goldfinger says the southern end of the fault – from about Newport, Ore., to northern California – has a 37 percent chance of producing a major earthquake in the next 50 years. The odds that a mega-quake will hit the northern segment, from Seaside, Ore., to Vancouver Island in British Columbia, are more like 10 to 15 percent.
“Perhaps more striking than the probability numbers is that we can now say that we have already gone longer without an earthquake than 75 percent of the known times between earthquakes in the last 10,000 years,” Goldfinger said. “And 50 years from now, that number will rise to 85 percent.”
Earthquake Preparedness Checklist (EPC)* – Use this earthquake preparation checklist to help prepare you and your families for an earthquake.
Eliminate potential hazards in classrooms and throughout the site:
____ Bolt bookcases in high traffic areas securely to wall studs ____ Move heavy books and items from high to low shelves ____ Secure and latch filing cabinets ____ Secure cabinets in high traffic areas with child safety latches ____ Secure aquariums, computers, typewriters, TV-VCR equipment to surfaces, such as by using Velcro tabs ____ Make provisions for securing rolling portable items such asTV-VCRs, pianos, refrigerators ____ Move children’s activities and play areas away from windows, or protect windows with blinds or adhesive plastic sheeting ____ Secure water heater to wall using plumber’s tape ____ Assess and determine possible escape routes
Establish a coordinated response plan involving all of the following:
____ Teach children about earthquakes and what to do (see resource list below) ____ Practice “duck, cover, and hold” earthquake drills under tables or desks no less than 4 times a year
____ Post, or make available to parents copies of the school earthquake safety plan (including procedures for reuniting parents or alternate guardians with children, location of planned evacuation site, method for leaving messages and communicating) ____ Enlist parent and community resource assistance in securing emergency supplies or safeguarding the child day care site: ____ store a 3-day supply of nonperishable food (including juice, canned food items, snacks, and infant formula) ____ store a 3-day supply of water and juice ____ store food and water in an accessible location, such as portable plastic storage containers ____ store other emergency supplies such as flashlights, a radio with extra batteries, heavy gloves, trash bags, and tools ____ maintain a complete, up-to-date listing of children, emergency numbers, and contact people for each classroom stored with emergency supplies
Involving child day care personnel and local emergency agencies:
____ Identify and assign individual responsibilities for staff following an earthquake (including accounting for and evacuating children, injury control, damage assessment) ____ Involve and train all staff members about the earthquake safety plan, including location and procedure for turning off utilities and gas ____ Contact nearby agencies (including police, fire, Red Cross, and local government) for information and materials in developing the child day care center earthquake safety plan
*For more free resources contact: (1) Federal Emergency Management Agency (FEMA) (2) Office of Emergency Services (OES) (3) Red Cross