By the time the warning went out, the waves were already landing.<\/p>\n
Last September, a fault slipped just west of Illapel, Chile\u2014a magnitude 8.3 earthquake<\/a> that launched waves ripping across the Pacific. Chile\u2019s coastal communities, just 50 kilometers away, were on the front lines.<\/p>\n Having learned from previous earthquakes<\/a>, Chilean officials quickly ordered an evacuation. Sixteen minutes after the fault ruptured, some one million Chileans were told to flee<\/a>. But by then, the waves had already begun to crash onshore\u2014and even with the delay, the warning was incomplete. Officials had underestimated the earthquake\u2019s strength and they couldn\u2019t hazard a guess about the height of the waves bearing down on them. By the time they got it right and added a regional forecast, 15 more minutes had passed. By the end of the day, 13 people had died<\/a>.<\/p>\n The tsunami warning was fast, but not fast enough. Seismologist Diego Melgar<\/a> thinks he can do better.<\/p>\n In a new paper<\/a>, Melgar and his colleagues argue that by using a new analytical technique they could have issued a forecast for the Illapel tsunami just two minutes after the ground stopped shaking\u2014a full 12 minutes before the waves hit the shore. Similarly speedy warnings would have been possible for Chile\u2019s 2010 and 2014 quakes and Japan\u2019s 2011 T\u014dhoku quake, they say, had their system been in place.<\/p>\n Crucially, Melgar\u2019s method doesn\u2019t require any expensive new equipment: it\u2019s simply a new way of analyzing and interpreting existing data. That means the technique could be rolled out quickly, and with little cost. The method uses common onshore GPS sensors, which track slight movements in the surface of the earth. More complex tsunami detection networks, such as the one operated by the US National Oceanographic and Atmospheric Administration (NOAA), rely on seismometers and expensive floating buoys.<\/p>\n \u201cWhat we\u2019re proposing \u2026 can be done now, today,\u201d Melgar says. \u201cWith only a few stations, you can make a very rapid assessment of the earthquake\u2019s size, and those [stations] exist everywhere now.\u201d<\/p>\n By watching GPS sensors jiggle, Melgar\u2019s new algorithm estimates what happened when the fault slipped, then models how the quake warped the seafloor, and simulates the ensuing tsunami. Within a few minutes, it pops out a color-coded map of the predicted at-risk coastal regions. Green means waves may be lapping at your knees, yellow predicts waves under a meter tall, and orange could signal a large tsunami up to three meters. Illapel, Chile and nearby cities would have seen red, indicating a wall of water three or more meters tall could be coming their way.<\/p>\n Melgar\u2019s team thinks showing the public a quick estimate of where waves will likely be dangerous is warranted. In studies of Japan\u2019s T<\/a>\u014dhoku tsunami<\/a>, the biggest factor determining who survived was simply when<\/em> they started to move.<\/p>\n