Walking to higher ground at a quick pace could be the key to survival for thousands of Americans if a large tsunami were to hit the Pacific Northwest, a new study published in the Proceedings of the National Academy of Sciences finds. The study focused on the high-risk communities within a 700-mile Northern California-to-Washington stretch of coastline that would be affected by a Cascadia Subduction Zone earthquake. Researchers found that nearly 5,600 additional residents—or another 6% of the population—would make it to safety in time if they walked to higher ground at a speed of 3.4mph rather than 2.5mph. At 2.5mph, 21,562 residents would be at risk, PhysOrg reports; the researchers put the population of the communities that could be affected by a CSZ quake at 94,872.
Researchers noted that the first tsunami wave from a CSZ quake would likely hit California and Oregon within 15 minutes. "Just by getting people to move faster, you can save thousands of lives," lead author Nathan Wood tells the Seattle Times. But others are pretty much doomed, per the Times, which reports that the study shows many of those living in Ocean Shores, Wash., and Seaside, Ore., wouldn't be able to evacuate in time even at the faster speed. In these cases, the research team suggests building strong-walled vertical evacuation centers and launching emergency preparedness campaigns. (Some towns are already heeding this advice.) The Pacific Northwest Seismic Network notes that the CSZ has produced 9.0-magnitude quakes in the past and tends to release a quake at intervals of 400 to 600 years; its last major one was in 1700. (Evidence of a "monster" tsunami was recently found in Hawaii.)