Earthquakes suggest new tectonic plate is forming

(CBS News) A new study suggests that two recent earthquakes may indicate a literal seismic shift in our understanding of tectonic plate movements.

Massive earthquakes under the Indian Ocean that took place last spring are the largest of their kind ever recorded. The 8.7 magnitude quake, followed by a 8.2 magnitude aftershock, could signal the formation of a new plate boundary under the Earth.

While not the largest earthquakes ever recorded, the two quakes are notable for their unusual location. The majority of earthquakes are known as thrust faults: massive sheets of rock sliding over or under another block along a fault line. The two earthquakes recorded in April were strike-slip faults, where one block of rock slides alongside another. The April quakes, which took place off the coast of Indonesia, are the largest slip-strike faults ever observed.

Additionally, the two earthquakes took place within a plate, rather than on its edge. According to a study published in the journal Nature, the quakes were part of the breakup of the Indian and Australian subplates under the Indian Ocean. The study also increased the magnitude of the initial earthquake to 8.7 - a significant increase in power as the Richter scale which is used to gauge the magnitude of earthquakes increases logarithmically rather than linearly.

Researchers believe the earthquakes were the result of the Indo-Australian plate rending itself apart. Seismologists have suspected the plate might be breaking apart since the 1980's. But the April earthquakes are the clearest evidence yet of this phenomenon. As one scientist wrote, "The long-term scenario is that a nascent plate tectonic boundary is forming: the Australian plate is becoming detached from the Indian plate."

This detachment will take several million years to complete, but research suggests more earthquakes like the ones in April will become increasingly likely in the future.