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Predict Your Risk in Seattle's Big Earthquake

The city released an online map tool for natural hazards.

The Really Big One,” the New Yorker’s July feature story on the predicted Cascadia earthquake, served as a wake-up call for many Seattleites. According to the Seattle Times, the article—and its apocalyptic overtones—sent residents “flocking to public-information sessions and home retrofit classes” and sparked a “boomlet” in sales of earthquake survival kits.

Now there’s an easy way for concerned citizens to evaluate their risk: the Seattle Natural Hazard Explorer, an online tool recently released by the city’s Office of Emergency Management. Simply scan the maps or search for an address to see just how vulnerable you are to a range of natural disasters—not only earthquakes, but tsunamis, landslides, flooding, and liquefaction, too.

(Seattle Office of Emergency Management)

The maps give you a sense of the dangers at a glance, but you’ll have to drill down into the definitions to understand them and their potential impact on infrastructure. In the top map, the colors don’t correspond to the intensity of ground shaking per se; they indicate the percentage of the force of gravity that has a 10 percent chance of being exceeded in that area in 50 years. (Think of it this way: In order for an object to go flying, the force from shaking has to exceed the force of gravity pressing down on it.) In other words, if you live in a zone labeled 80 to 110 percent, then there’s a 10 percent chance that an earthquake will shake your house with between 80 and 110 percent of the force of gravity at some point in that 50-year period. For reference, “dishes, windows, and doors [can be] disturbed" at about 1.4 to 4 percent of gravity.

But don’t just use these maps to satisfy your morbid curiosity. Use them as a tool to get prepared for the big one.The city’s Office of Emergency Management offers a number of tips to get started. (Kathryn Schulz, the author of that harrowing New Yorker article, followed it up with advice of her own.) Think carefully about where you rent or buy a home, and always have an escape plan.

As one disaster expert told the Seattle Times, “It’s up to the people to decide their risk tolerance.”

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