April earthquake near Sumatra puzzles scientists

Science : The 8.6-magnitude earthquake that occurred 11 April off the coast of Sumatra may have been both the largest strike-slip earthquake and the largest intraplate earthquake ever recorded. Its power and location took seismologists by surprise. Usually, the largest earthquakes occur on the largest faults, but this one occurred not on a major plate boundary but rather adjacent to it. Because the Sumatra quake was the latest in a series of large intraplate strike-slip earthquakes in oceanic lithosphere, it provides scientists an opportunity to study the physics of such earthquakes and to determine how best to assess the potential hazards. Jeffrey McGuire of the Woods Hole Oceanographic Institution and Gregory Beroza of Stanford University look at the complex geology at the bottom of the Indian Ocean in their article published today in Science.