Unusual Series of Quakes Indicate Tectonic Breakup in Indian Ocean

Two massive earthquakes in April in the Indian Ocean and an unusual series of aftershocks may signal the formation of a new tectonic plate boundary within Earth’s surface. Reporting in the journal Nature, French scientists say that an analysis of the two April 11 earthquakes — one of magnitude 8.6 and the other of magnitude 8.2 — shows that they were not typical quakes that occur when one plate slides under another or two plates slip horizontally along a fault line. Instead, the earthquakes, caused by breaks along four faults in the Indian Ocean and accompanied by an unusually large number of aftershocks, indicate that the Indo-Australian tectonic plate may be breaking up. “It’s the clearest example of newly formed plate boundaries,” said Matthias Delescluse, a geophysicist at the Ecole Normale Superieure in Paris. The researchers said that the massive and deadly 2004 Indian Ocean earthquake and tsunami, as well as another earthquake in 2005, may also have been related to the April quakes and the breakup of the Indo-Australian plate.