This shook us up

Eric, a writer for the Wallyhood blog gives a good explanation of the three types of earthquakes that could rock Seattle:

Like Nepal, and unlike California, we live in a tectonic plate crumple zone. At a broad level, California and Oregon are shoving us into Canada.

That crumple action means you can expect one of 3 types of earthquakes here. The most frequent and least serious type is like the 2001 Nisqually quake — deep underground, with movement that will knock over brick chimneys, topple TV’s, and maybe collapse aging viaducts or a building in Pioneer Square.

The second type is a magnitude 9 mega quake that will happen when the Cascadia Subduction Zone off the coast moves, similar to what happened in Japan. If that goes you will feel very long lasting and powerful waves from side to side, with most of the danger being to older, taller structures, plus tsunami flood zones along the coast.

Finally, the most dangerous type of quake here in Seattle is a shallow quake nearby, most obviously along the Seattle Fault, with violent shaking leveling older buildings in large numbers.

The Seattle Fault most catastrophically ruptured in AD 900, causing West Seattle to rise up by 20 feet relative to Wallingford and triggering tsunamis in Puget Sound. Regardless of the type of quake, Wallingford is fairly lucky compared to other parts of Seattle. We are not in a slide zone and are not on top of an old lake bed that is likely to liquefy during the quake, so we won’t suffer from the worst amplified shaking.

See the whole post with images on Wallyhood. One person commenting says they’ll be using Green Lake in emergencies as a potable water source (using camping filters). Would Lake Union also work? Not likely according to another commenter, Anna, who experienced the Christchurch Earthquake and has this advice about being prepared:

1. All natural water bodies will be contaminated with raw sewage. If a big quake damages the sewer network, the least worst solution is to pump the overflows into the nearest natural water body (so it doesn’t back up through people’s toilets). IF water has to be trucked in, it will need to be boiled or treated before drinking, so you will be able to use your camping gear then. Just remember – you can’t filter whats not coming out of the tap. Have some bottled water in the house.

2. How will you get home? Multi-story parking garages will be off limits pending structural assements, so your car will be stuck for 2-3 months. Unless the city is training transit workers to be emergency responders, buses will probably stop (as it did in CHCH), trains will have to stop, pending line inspections. Christchurch (pop 400,000) is flat, with a regular grid of streets. Complete gridlock set in within 15 minutes. a half hour drive through the least affected parts of the city took 2-3 hours. Travel times into the worst areas were up to 12 times longer than usual.

3. Who will get the kids (or grandma)? All three million people in the area are going to be trying to check on thier families and friends. Don’t expect to get a dial tones. Texts will probably go through, but with long delays, and may arrive out of order. Have a plan you can implement without talking to your partner.

4. Keep some cash in the house. Even in a really big quake the city will not be uniformly flattened. some buildings will be fine and some will be destroyed. Those shopkeepers who can open, will, but they won’t be able to process plastic.

Finally, a ‘zombie apocalypse’ is funny joke, but it’s a poor model for disaster response. Humans are social animals. connecting with others is how we make sense of what we have experienced. Those who have come through in good shape will want to acknowledge their good fortune by lending a hand, but top-down emergency management organizations are ill-prepared to handle these impulses.

In case you missed it, Mossback’s piece on Crosscut provides a personal and historical look at Seattle’s past earthquakes. And for more unsettling insights, both Mossback and Eric recommend the book Full-Rip 9.0 .