Worst-case scenario Northwest earthquake – Full Rip 9.0
On a calm day, glancing across the water to the west of Seattle, it’s easy to forget the stately Olympic Mountains were created by a collision of tectonic plates off the Washington coast.
The movement that thrust the mountains into existence could be the source of a mega earthquake in the region “at any time.”
“A new scenario just came out [Tuesday] looking at some of the potential effects of a magnitude 9.0,” says Sandi Doughton, science reporter for The Seattle Times. “There could be more than 10,000 people killed, 30,000 people injured and damage to infrastructure that takes years to repair.”
Doughton, who’s been researching earthquakes in the Northwest for 20 years, is author of a book with an ominous title – “Full Rip 9.0.”
“It comes from the description of probably our worst-case scenario earthquake, and that would be an earthquake that rips the full length of the 700-mile fault off the coast called the Cascadia Subduction Zone,” Doughton says.
The 700-mile fault she’s referring to is about 50 miles out to sea off the coast.
It stretches from British Columbia, through Washington and Oregon, and to Northern California. It’s where the Juan de Fuca geologic plate is sliding under the North America plate.
The process, which started about 20 million years ago, is pushing North America over Juan de Fuca at a rate of about 1.5 inches a year.
These are not smooth dinner plates gliding across each other and stacking neatly like dishes in a cupboard. These tectonic plates stick, resist, shift and bash together creating earthquakes.
The last rip along the fault was about 300 years ago, when the entire 700-mile stretch slipped in the span of about five minutes, creating a magnitude 9.0 earthquake and a massive tsunami occurring in January of 1700.
Another fault, the Seattle Fault, runs from SoDo to Issaquah. It only started to gain researchers’ attention in the 1980s. Its full extent and connection to other faults is still being mapped.
Scientists estimate a 6.7 quake on the Seattle Fault could kill 1,600 people, injure 24,000, destroy 10,000 homes or buildings and damage another 180,000.
That’s far worse than the last quake most of us remember – the 6.8 magnitude Nisqually Quake of 2001.
Archive audio captured the moment at 10:54 on the morning of February 28, when my radio partner Dave Ross was on the air with his talk show taking listener phone calls.
“Oh hi, Dave, um…”
“What are we having here, are we having an earthquake?” Ross interrupted. “We are shaking like crazy here. We are having an earthquake, I believe. The lamps are shaking here. We are rocking and rolling ladies and gentlemen.”
About 400 people were injured that day and there was significant damage to older brick buildings in Seattle and other cities in the Puget Sound area.
The Nisqually quake shook up city planners.
“For example, the City of Seattle really took seriously the issue of what would happen to all the fire stations,” Doughton says. “A lot of them were old and seismically unsound and in a big quake the doors would have been stuck shut and firefighters wouldn’t have been able to get out if they had survived the quake.”
Still on the city’s earthquake to-do list is reinforcing old brick buildings.
“We have almost 1,000 of them here in Seattle and the city is just beginning to look at a requirement that those be retrofit in some way,” she says.
Doughton’s research leaves her critical of state planners who haven’t paid enough attention to transportation and infrastructure needs in the event of a major earthquake.
The State of Washington also hasn’t surveyed the soundness of public schools, she says.
Our state does regularly promote earthquake drills, including The Great Shake Out drill last Thursday involving over 800,000 Washington residents as well people from around the world.
A more promising idea is in the science of trying to predict earthquakes.
The 9.0 quake that shook Japan in March of 2011 has yielded research that might help scientists in the Northwest.
“They have a lot of seismometers and other instruments that can measure tiny amounts of movement on the sea floor. They didn’t realize it at the time they had to go back and look at the data, but there was some movement going on,” says Doughton. “That probably was a precursor to that big earthquake.
Washington has two sensors on the sea floor off our coast serving as a possible early warning system.
Funding to place more seismometers off the Pacific coastline from Washington to southern California has been cut over the years.
By LINDA THOMAS