'The Big One' Is a Big Problem for Old Seattle Houses

Tom E. Hall, a seismic retrofitter, teaches homeowners in Seattle how to bolt a house to its concrete foundation.
Tom E. Hall, a seismic retrofitter, teaches homeowners in Seattle how to bolt a house to its concrete foundation. (By Blaine Harden -- The Washington Post)
By Blaine Harden
Washington Post Staff Writer
Friday, November 24, 2006

SEATTLE -- "We got problems here."

So explained Craig S. Weaver, a seismologist for the U.S. Geological Survey and chief of its Pacific Northwest earthquake studies project. "There will be earthquakes. You can take that to the bank."

This is not what you want to hear if you have taken much of your life savings out of the bank -- as I have -- and bought an old house in Seattle.

Alone among U.S. cities, Seattle has the dubious distinction of having had since 1949 three damaging earthquakes that toppled brick buildings and caused some low-lying ground to turn into a sandy liquid. But there is even more worrisome news. Seismologists have learned that Seattle, like Los Angeles and San Francisco, might have a Big One in its not-too-distant future.

A rupture along the Seattle Fault, which runs under the south end of the city and was unknown until 1992, would kill 1,600 people, injure 24,000 others, destroy 9,700 buildings and damage about 180,000 other structures, according to a scenario put together by earthquake experts and published last year with funding from the state of Washington.

Big Ones occur here about every thousand years, much less frequently than in California. The last one occurred in what is now Seattle 1,100 years ago. By the geologic clock, this city is due for a catastrophic shake that the builder of my old house had no idea was even a remote possibility. About a quarter of a million houses in and around Seattle are in the same fix.

What's an anxious homeowner to do?

The answer in Seattle -- as across the earthquake-prone West Coast -- is surprisingly simple to explain: Bolt that old house to its concrete foundation.

Structural engineers say that even an old wooden house is strong enough and flexible enough to survive a major earthquake without serious structural damage -- if it is not shaken off its foundation. In this part of the country, most houses built after 1975 are bolted down.

My house was built in 1904.

So it was that I called 877-2-BOLT-IT, and on a recent Saturday afternoon attended a home retrofit class sponsored by the city of Seattle.

Tom E. Hall, the volunteer instructor, is a 30-something seismic retrofitter with a shaved head and a thin, agile body. He had hauled into the auditorium of a local library a simulated concrete basement foundation wall and an dizzying array of power tools, bolts and anchor plates.

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