Old fractures caused rare 8.6 magnitude earthquake



The 8.6 magnitude earthquake that occurred on 11 April 2012 100 kilometers off the coast of Sumatra was unusual in that it originated within the plate rather than at a plate boundary. In fact, it is the largest such earthquake in observed human history. The quake originated under the Wharton Basin in the Indian Ocean, where hundreds of kilometers of rock were under crushing tension, causing the plate to deform at its base. However, this deforming zone also absorbed tension as two plates, the Indian and Australian plates, rotated toward each other.