© USGSThe red star marks where the quake hit.
The magnitude 8.6 earthquake that struck in the Indian Ocean off the western coast of Sumatra today resurrected fears of a repeat of the 2004 Indian Ocean earthquake and tsunami that proved one of the most devastating natural disasters in modern memory.
However, this earthquake, which struck at 2:38 p.m. local time (4:38 a.m. ET), about 270 miles (435 kilometers) off the coast of the Indonesian island was a different animal altogether than the
2004 earthquake and tsunami, which killed more than 230,000 people and left millions homeless.
"It was quite a bit smaller," said Julie Dutton, a geophysicist with the U.S. Geological Survey. The 2004 quake was a magnitude 9.1 - the third most powerful earthquake ever recorded.
Perhaps more significantly, today's earthquake was a different kind of quake all together. Instead of occurring at a plate boundary along
an area called a subduction zone, where one tectonic plate is diving beneath another, this earthquake occurred in the middle of an oceanic plate, where the faults in the crust essentially moved from side to side instead of up and down. These sorts of events are called strike-slip earthquakes.
"With a strike-slip event you don't have the same potential hazard for a tsunami as you do with a subduction event because the plates are moving adjacent to each other," Dutton told OurAmazingPlanet.