"The T waves for the Sumatra earthquake were captured by underwater microphones located at Diego Garcia, more than 1,700 miles from the epicenter. These microphones are part of arrays known as hydroacoustic stations that are scattered throughout the world's oceans to listen for the telltale sound of an atomic blast."
"We can hear icebergs cracking and magnitude four earthquakes underwater from across the ocean basin, so it's not surprising that we heard this earthquake," said Tolstoy.
http://www.ldeo.columbia.edu/news/2005/07_20_05.htm
http://www.ldeo.columbia.edu/news/2005/images/tsun_eq.mp3
"We can hear icebergs cracking and magnitude four earthquakes underwater from across the ocean basin, so it's not surprising that we heard this earthquake," said Tolstoy.
http://www.ldeo.columbia.edu/news/2005/07_20_05.htm
http://www.ldeo.columbia.edu/news/2005/images/tsun_eq.mp3