Would the U.S. tsunami warning system have averted Indonesia’s disaster?
By Robinson Meyer
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“There’s this idea that the [early-warning] system will provide some useful warning to you, if you’re on the beach, directly adjacent to the fault line, and that’s not really true,” [Chris Goldfinger, a professor of geophysics at Oregon State, says]. “In most cases, if you’re on a coastline that has a big subduction zone, the earthquake is the warning.”
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The stopwatch, that is, for the tsunami. If the Cascadia quake lasts for two minutes, it could spawn a 15-foot tsunami. If it lasts for longer than that—and the ground could shake for up to six minutes—it could unleash a wave “on the order of 90 feet,” Goldfinger told me.
But how would we know this wave is coming? Most of the U.S. early-warning sensors sit relatively offshore. If Cascadia triggered a tsunami, its point of origin would likely sit between the coastline and that array of tsunami sensors. So any wave would have to travel out to sea before it could be detected by a U.S. government sensor. Even once it’s detected, news of the wave must still be transmitted to a satellite, sent back down to Earth, and reviewed by a person in the U.S. tsunami center before, finally, resulting in an official early-warning alert.
This whole process could take three to five minutes, Goldfinger told me. Meanwhile, the inbound wave would be approaching the coast. He warned that beachgoers near the epicenter of a future quake may only have 15 minutes before the tsunami strikes. So if you feel violent shaking, but don’t evacuate until you get a tsunami early-warning alert, you may have burned up a third of your time.
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