Eerie sounds of Earth's rupture

A sound track of the Earth ripping apart during December's massive Indian Ocean earthquake and tsunami is adding to the body of scientific evidence from last year's momentous natural disaster.

Scientists at Columbia University's Lamont-Doherty Earth Observatory are poring over audio of the 9.3 quake along the Sumatra-Andaman Fault. The audio came from a little-known and sometimes hard-to-access source: a global network of instruments that monitor compliance with the Comprehensive Nuclear Test Ban Treaty.

The devices that recorded the devastating temblor were located in Diego Garcia, an island more than 1,700 miles from the epicenter of the quake. The Columbia University site has a link to the audio, which sounds like a vague rumble.

"It's really quite an eerie sound to hear the Earth ripping apart like that," said Maya Tolstoy, a marine geophysicist at Lamont-Doherty. "We hear it on smaller earthquakes quite frequently but something of this scale that goes on for eight minutes is very much unprecedented."

Tolstoy--whose research appears in the July/August issue of Seismological Research Letters--said the sound track offers insight into the rupture, which is believed to span about 750 miles.

"What we are able to see is very clearly two phases in the speed of the rupture," Tolstoy said. "The first third is much faster, the second two thirds slower. We are able to tell how long it ruptured, how fast it went, and those are important things to know for disaster mitigation."

Because hydroacoustic stations like the one at Diego Garcia operate around the clock, Tolstoy believes they may hold the potential to provide a rapid and accurate source of information on the duration and length of an underwater earthquake. Such information is critical to determining where to send emergency relief in the first hours of a disaster, as well as in determining the risk of a tsunami.

Improvements to computing power have put real-time seismological information at researchers' fingertips and helped advance quake warning systems around the globe.