The 2011 earthquake that rocked Japan and sent a devastating tsunami sweeping down the country's coast may have had help from a huge undersea landslide, an international team of researchers says. If confirmed, the scenario could explain why waves along one 100-kilometer stretch of coastline topped 40 meters—four times as high as elsewhere in Japan—and claimed about a quarter of the tsunami's 18,000 victims. Other geoscientists had proposed that an undetected second earthquake triggered the monster waves, but the authors of the new study were unconvinced. Working backward from water motion recorded by shoreline gauges on the day of the earthquake, they conclude that a slab of sediment the size of Paris slid down the steep slope of the Japan Trench near the northern end of the 2011 rupture, acting like a piston to amplify the tsunami. |
