The western United States is overdue for a huge earthquake and tsunami and is nowhere near ready to cope with the disaster, experts say.
A volatile, horseshoe-shaped area known as the Pacific Ring of Fire has recently erupted with quakes in Chile, Japan, Mexico and New Zealand, and seismologists say it is just a matter of time before the next big one hits.
Twin fault lines place the US west at risk: the San Andreas fault that scars the length of California and the lesser-known but more potent Cascadia Subduction Zone off the Pacific Coast.
A 9.0 quake in this underwater fault that stretches from the northern tip of California all the way to Canada’s British Columbia could simultaneously rattle the major port cities of Vancouver, Portland and Seattle, unleash a massive tsunami and kill thousands of people.
“From the geological standpoint, this earthquake occurs very regularly,” says engineer Yumei Wang, who is the geohazards team leader at the Oregon Department of Geology.
“With the Cascadia fault, we have records of 41 earthquakes in the last 10,000 years with an average of 240 years apart. Our last one was 311 years ago so we are overdue,” she says.
Records from the last Cascadia quake in 1700 AD show that the tsunami it generated was so powerful that it killed people in Japan.
“Geologists can’t predict exactly when the next earthquake will be but engineers can predict the damage pattern,” says Wang.
Buildings at risk
Major efforts to retrofit buildings have been underway for decades in western states, but many coastal schools, hospitals and fire and police stations are still housed in older buildings and remain at risk.
In the case of a tsunami, experts are also concerned about old structures and elderly or ill people who may live near the water and may be unable to escape a swelling wave.
“Quite frankly some of our coastal communities are extensive enough and flat enough that moving inland and uphill is not possible. It is just too far to go,” says Wang.
Engineers have devised a concept for a tsunami shelter where residents could seek higher ground without travelling far inland, but none have yet been built for public use.
“All preparedness is local and it varies dramatically over the length of the coast,” says Tom Tobin, president of the Earthquake Engineering Research Institute.
“We are not at all even close to being as prepared the way the Japanese were, and yet you can see the devastation that occurred,” he says.
“I think in the United States we have a hard time convincing people there is a real danger that lies out there on the Pacific northwest coast.”