- Don't like the look of this old town
What goes up must come down
—Public Image Limited, "Seattle"
Washington is called the Evergreen State for its lush forests. Seattle, its largest city, is a great tourist destination and the region a beloved home for millions of people. But that land owes its very beauty to a highly active, even violent geologic setting. The large earthquake that struck the area on February 28, 2001, was just a reminder of that state of affairs. This time, not a single person was killed. Seattleans should sleep better now, knowing that earthquake preparation really pays.
Seattle's Geologic Setting
But first a word about where Seattle sits. Western Washington is a part of the North American crustal plate that is overriding the smaller Juan de Fuca plate (see "Subduction in a Nutshell"). The little plate is not much of an obstacle, being composed of low-lying oceanic crust, but the friction between the plates still raises some very large earthquakes of magnitude 8 and 9. Not often—the last one was in 1700, recorded in Japan as a large tsunami—but these great subduction earthquakes are impossible to predict. And there are lots of smaller quakes, too, in the 6 to 7 magnitude range. The 2001 quake was a 6.8.
As the big plate forces the little plate deeper into the mantle, parts of it turn to magma and make their way to the surface (see "Arc Volcanism in a Nutshell"). Thus we have the Cascade Range, a series of large volcanoes that stretches from the Canadian border down to California. The range gives its name to the whole region—Cascadia. Volcanoes bring fresh rock to the surface, which weathers into rich soils, and the mountains also catch plenty of Pacific rain. And there's your Evergreen State—lovely, like the rest of Cascadia, in the years between earthquakes and eruptions.
Seattle's Emergency Plans
Earthquakes are bad news anywhere, of course, but in Seattle they can be especially severe because Cascadian subduction quakes can be so large. The challenge to emergency planners is great. One creative approach to the challenge grew organically, starting one day when a small group of IT professionals from different firms got together to share notes about protecting their computer systems from earthquakes.
The group of geeks liked sharing advice in an informal, trusting atmosphere. Over the years their talks expanded into other emergency-response issues, and municipal agencies got involved too. The group took the name CPARM, for Contingency Planning and Recovery Management Group. Recently CPARM launched a series of public/private mitigation programs, aimed at preventing damage cheaply today to avoid repairing damage expensively tomorrow. Strengthening houses, evaluating school buildings, compiling long-term landslide maps, and placing strong-motion seismometers in structures are all elements of this effort.
The emergency-response community also pays attention to risks from the local volcano, Mount Rainier. One of the highest and handsomest mountains in the 48 states, Rainier has covered the countryside with hot, choking ash many times in its million-year history. Its glaciers and its steep slopes weakened by hot, corrosive volcanic gases have combined to make gigantic mudflows (lahars) and avalanches. About 5,600 years ago, one of these mudflows reached the Seattle area, many miles away. And the city is underlain by more ancient mudflow deposits, interspersed with beds of ash.
Even a centimeter of ash is a serious inconvenience, scratching the finish of cars, killing tender plants, blowing in the wind to threaten people's respiratory health, and turning to gritty mud in the rain. A severe ashfall would paralyze Seattle for many days in a gray, choking misery like no other kind of natural disaster.
With federal help, the city responded to this prospect by training the people to rely on themselves, block by block. The most important thing to get people through a civic emergency, I've been told, is to have something for everyone to do. Seattle's program relies on checklists and simple drills to get people involved with taking care of their neighborhood in a well-organized way. Take a look and you may see things you could do where you live. Or, if you're visiting Seattle when the worst happens, you'll be ready to find a role and fill it—and you'll sleep well.
Seattle's situation is repeated up and down the Pacific Coast throughout Cascadia. You'll see in this U.S. Geological Survey plot that most of the Cascade volcanoes are dangerous, having erupted during the last 4,000 years.
PS: The federal agency FEMA had a thriving preparedness program called Project Impact. In Seattle, it funded and coordinated much of the work I've featured in this article. Project Impact was discontinued after President Bush declared that it hadn't shown any benefit—one day before the 2001 earthquake.