Whole lotta shakin'

For me, the earth last quaked on February 28, 2001. I was at work when the building began swaying. I knew immediately what was happening and dove under my desk. Seconds later, from that undignified vantage, I peeked out the window only to see the building across the street moving back and forth, in a stately manner, across my field of vision. It was not a reassuring sight.

It was a 6.8 earthquake, lasting about 45 seconds.

To me, an earthquake is worse than most other disasters. The experience is hallucinatory. When the earth itself moves, you've lost your fixed frame of reference. You feel you're in free fall until the shaking finally stops. While it lasts, you're not sure when, if ever, it will end. Or how much worse it will get. Or what will be left of your world when you finally make it through to the other side.

Seattle sits on several seismic faults, along which seismic pressure can cause sudden slippage. One, the shallow Seattle fault, passes through town about a mile from my house. That particular fault was responsible for a major earthquake at a shallow depth in about A.D. 900 or so. Indian legends about that quake still circulated a thousand years later. The same earthquake today would be devastating.

The 2001 earthquake that so discombobulated me was not the result of slippage along the shallow east-west Seattle fault. It was caused by the continuing eastward movement of the Juan de Fuca tectonic plate as it tries to burrow under ("subduct") the continental plate. It is blocked from movement when it hits the Cascade mountains, causing it to crumple the landscape like the hood of your car running (very slowly) into a brick wall. Eventually, pressure builds up and at some point the plate ruptures at a deep location. In 2001, pressure was released by a rupture at a considerable depth, down near Olympia. Our shaking up here in Seattle was intense, but, because of the distance from the break and the depth at which it occurred, the actual damage was not that great. (Relatively speaking -- estimated costs were $2 billion.)

The quake of the same intensity caused by slippage along the shallow Seattle fault -- again 6.8, but at a shallow depth and underneath Seattle itself -- would cause immensely more damage.

We also may be due for a subduction earthquake, caused by release of pressure where the two plates come into initial contact. This could well be a 9.0 earthquake, similar to Japan's, but it would occur off the coast, a relatively long distance from Seattle and from other major population areas. The last subduction event in this area, a 9.0 earthquake, occurred in about 1700.

From a scientific point of view, this is all quite interesting. But I picture my poor little house -- probably not flattened, but knocked off its foundations with perhaps the loss of its brick facing. Earthquake insurance is prohibitively expensive. I simply roll the dice from year to year, praying each year that the dice won't come up 7.

I should have my house retrofitted, I suppose. I should fill the basement with canned foods and beverages. I should have handy a battery powered radio. Maybe I should sell the house and rent an apartment? Let someone else worry about the damage when the Big One happens?

This week's disaster in Japan has inspired me. I've filled an empty one-gallon milk container with water and stored it in the basement. Well, it's a start.