Three earthquakes, not one, caused Samoan disaster last year

Nature : Last year’s largest earthquake took place on 29 September in the Samoan islands and, with its 12-meter-high tsunami, killed 192 people in American Samoa, Samoa, and Tonga. As Nature‘s Richard Lovett reports, evidence from buoys tethered to the sea floor, seismographs, and GPS monitors indicates that the seismic disturbance consisted of three earthquakes: one of magnitude 8.1, which struck first, and two of magnitude 7.8, which followed in the next two minutes. The mostly horizontal displacement of the 8.1 quake would not have unleashed a deadly tsunami on its own, but it did trigger the other two quakes, whose mostly vertical displacement caused the tsunami.