Dan Callister / Getty Images file
Located just 50 miles off the coast, the 680-mile-long Cascadia fault has lain dormant for 300 years. When it wakes, it could trigger an earthquake and tsunami similar to the one that struck Japan today.
As the world tunes in to the disaster following the earthquake and tsunami in Japan today — and with waves rattling nerves along the U.S. West Coast and Hawaii — a question rises to the fore: Could such a disaster happen here?
The short answer is yes. It already has. Major quakes of a similar style rupture along the 680-mile-long Cascadia subduction zone, a fault that runs from Northern California to British Columbia, every few hundred years. They trigger tsunami waves reaching up to 15 feet high that hit the shore about 10 to 15 minutes later.
The fault last ruptured in 1700 – a magnitude-9 event that sent tsunami waves crashing into Japan. Experts believe it is a matter of when, not if, the next one will happen, according to Brian Atwater, a geologist with the U.S. Geological Survey and the University of Washington and an expert on the 1700 event.
"There's no reason to question the history here," he told me today.
Recent computer simulations of a hypothetical magnitude-9 quake on the Cascadia subduction zone found that shaking could last two to five minutes, strong enough to collapse poorly constructed buildings and damage highways and bridges. Powerful tsunami waves could rush ashore minutes later, potentially devastating coastal communities.
The threat is greatest along the northern part of the West Coast. Caltech seismologist Kate Huttontold MSNBC today that Southern California doesn’t have subduction zones like the Cascadia fault.
According to calculations by Chris Goldfinger, a geologist at Oregon State University, there's an 80 percent chance that the portion of the fault off southern Oregon and Northern California would break in the next 50 years. The odds are lower — 27 percent for the same time period — for Washington state and Canada's Vancouver Island.
"People try to compute these earthquake weather forecasts by taking into account 300 years have passed since the last one and the fault has been busy putting money in the bank to spend on the next earthquake," Atwater explained. "So the more time that passes, the better the car the fault can buy."
Even though authorities have been aware of the risk for years, the Pacific Northwest is not adequately prepared, according to geotechnical engineer Yumei Wang of the Oregon Department of Geology and Mineral Industries.
"People are in a really dangerous position," Wang told Discovery News in 2009. "This is going to happen, and it's going to have really bad ramifications unless we do something."
She has proposed building a series of tsunami shelters up and down the coast. As well, work is ongoing to shore up schools, hospitals and other buildings. Similar efforts are under way in Seattle, Brian Gaff of the city's Office of Emergency Management, told the AP.
Part of the problem is that scientific knowledge about the Cascadia subduction zone is way out in front of public policy, laws and building codes, Edward Wolf, a private consultant and writer in Oregon who works closely Wang, told me today.
"It's analogous to climate change. The science is considerably ahead of public awareness and policy response," he said.
To date, attention has been put into mapping tsunami inundation zones, plotting evacuation routes and preparing signage to inform people about the risk. "But there are still some low-lying coastal areas with difficult access to evacuation that would be difficult to impossible to evacuate in the event of an earthquake," he said.
Proposals such as Wang's for shelters that can withstand tsunami waves have been floated. Another idea is to construct large earthen mounds that are high enough and accessible enough to serve as a tsunami refuge in regions such as southwest Washington's Long Beach Peninsula. None of these proposals has been funded.
Although the risk for an earthquake and tsunami like the one in Japan is very real for the West Coast, there is no scientific evidence to suggest that today's temblor will trigger a quake on the Cascadia subduction zone. But, as Atwater emphasized, "It's not a matter of if, but when, the next one will happen."
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John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).