Oh no! Not another “an earthquake is coming!” book. Yeah, but at least it’s not another earthquake apocalypse movie.
The problem with a book warning that Seattle sits on a fault zone, and has a shoving and grinding tectonic plate just offshore, is that we can’t do a damn thing about it.
(Unless you’re one of the few people with enough spare change to do seismic upgrades to your house; but what’s the point of owning the only house still standing in a flattened neighborhood, in a destroyed city with no functioning roads or utilities? Or, alternatively, you could move somewhere else. Such as Florida’s hurricane coast, or Oklahoma’s tornado alley — choose your poison. There’s probably no completely safe place on this planet.)
Seattle Times reporter and book author Sandi Doughton does the best thing possible to make this dull subject a readable book: She turns it into a detective story about how geologists identified the hazard, located the fault zones, and assessed the risks.The result is Full-Rip 9.0. I casually picked it up last week while browsing the library shelves.
Most of this took place from the 1980s onward; and it’s only in the last decade or so that scientists, emergency planners, and structural engineers have woken up to the fact that the Cascadia Subduction Zone, which runs from northern California to British Columbia, has the potential to produce earthquakes as strong as anywhere on earth.
In fact, we’ve already had a megaquake here. At 9 p.m. on January 26, 1700, the real estate on which Seattle now sits was shaken by an earthquake roughly the same strength as the 2011 Japanese 9.0 megathrust quake that killed nearly 18,500 people and collapsed or damaged a million buildings in the most earthquake-prepared nation on earth.
Making matters worse is that Seattle was built on top of a depression in the bedrock filled with glacial till (visualize a bowl filled with sand), in which the shock waves would reflect and reverberate, magnifying a quake’s destructive force.
How bad would it be? The experts think most of downtown Seattle’s tall buildings would survive, although some would have significant damage. Probably the safest structures are the stadiums and Space Needle. The stadiums, which sit smack-dab on top of the Seattle Fault, are new enough to have been designed specifically for the seismic risks, which by then were known. The Mariners stadium, for example, was built in modules that can shift like the expansion joints in a bridge.
The Space Needle was grossly overbuilt; the plans were worked on by a structural engineer who knew what he was doing. He used so much steel it increased the Needle’s original cost (which was $4 million, if you’re curious) by a third — it would sway in a strong quake, and people at the top would get a wild ride, but we’re assured it won’t fall down.
What are the chances? Seattle has had sizeable quakes before, in recent times the 1949 and 1965 quakes stand out, plus Seattle got a shaking from the 2001 Nisqually quake that damaged the state capitol dome in Olympia. These were all localized “deep quakes,” not the really “Big One.”
The Cascadia Subduction Zone’s last megathrust quake, a little over 300 years ago, is recorded in soil layers in alterations to the region’s physical landscape. Geologists can see where it moved the ground and created local landforms. We know exactly when it happened because its tsunami washed up on Japanese shores, and by 1700 A.D., Japan was a bureaucratic society that kept meticulous records. Which, in this case, were found in an old castle. (How they were found is part of Doughton’s detective story.)
Geologists have established that Cascadia seems to slip every 500 years or so, with really big shocks about every 3,000 years. This is more likely to happen when the plates lock tight and stresses build up. There is evidence that Cascadia is locked and priming for another abrupt slipping of the plates. No one knows when that might happen. Probably not in our lifetimes, so at this point, most people will quit reading this book review and go to sleep. According to Murphy’s Law, that’s exactly when Mother Nature will bite you in the ass.
There are things individual homeowners can do to shore up their houses, and Doughton touches on these, mostly in terms of how to find further resources. The main thing is to keep your house from moving on its foundation. This is done by bolting the sill plates to the concrete foundation. Most homes built in this area in the 1970s or later will be bolted down. My digs, built in 1965, have earthquake bolts.
Doughton also refers to “shear walls,” which provide lateral resistance to sideways movement. Diagonal bracing and plywood sheathing serve this function to some extent, but if you own an older home in the Seattle area (say, a 1940s bungalow or craftsman), you might want to have a seismic survey done to determine what specific bracing should be added to the structure, especially in the basement or crawl space.
The bottom line is that science can’t predict earthquakes, but we now have a much better understanding of the Pacific Northwest’s seismic risks, and it isn’t a pretty picture. This area was settled and built up before those risks were understood, and a 9.0 earthquake, when we get one, will do a lot of damage.
Doughton quantifies the relative power of earthquakes for us on page 120 of this 242-page book. The 2001 Nisqually quake, a 6.0, released energy equivalent to 240 kilotons of TNT; the 2011 Japanese quake, a 9.0, at 480 megatons was 2,000 times as powerful. The Cascadia Subduction Zone is now believed capable of producing 9.2 quakes, possibly higher. On the earthquake scale, a 9.2 is not incrementally but rather magnitudes stronger than a 9.0.
This fairly compact and informative book is a quick read — I finished it in 3 days — and it’s not boring. Doughton, a professional journalist, is good at storytelling and keeps the suspense going well enough to hold your interest. While the subject is not exactly earth-shakingly thrilling (waiting around for an earthquake to happen is even less exciting than watching grass grow or paint dry), the story of how scientists pieced together a picture of the geologic monster lying in wait beneath our feet makes for good fireside reading on dreary winter evenings.
If you have a few spare evenings, and you’re looking for something to read, you might consider this book.