Oceanic Sounds of Last Year's Earthquake

DoctorBit writes "Columbia University's Lamont-Doherty Earth Observatory is reporting that some of their researchers have analyzed recordings of the underwater sound produced by last year's magnitude 9.3 Sumatra earthquake. By studying the ocean's sound waves rather than the Earth's seismic waves, the researchers measured the earthquake's speed and duration with unprecedented accuracy."

Comments

Detecting Submarines

[reporter]

The phrase "unprecedented accuracy" seems to imply that this technique can detect very minute underwater sounds. Would this technology also be applicable to detecting the barely detectable sounds of underwater nuclear submarines?

Faaaast!

[Anonymous Coward]

The first phase encompassed the first three minutes of the eight-minute earthquake, during which the rupture proceeded north at about 1.7 miles per second (2.8 km/sec) from the epicenter. During the second phase, the rupture slowed to 1.3 miles per second (2.1 km/sec) and continued north for another five minutes until it reached a plate boundary where the fault changes from subduction to strike-slip, where the two plates push past one another in opposite directions.

For the astronomically challenged (my condolences) that would make 9.07417417e-14 and 6.80563063e-14 Parsec/s, respectively

192kbps

[E8086]

What are the chances the downloadable music industry can learn from this?
This freely downloadable mp3 is encoded at 192kbps, 50% higher than most if not all tracks available from the legal music download companies, which we pay for.
Now go and give the Red Cross some money for their continuing relief efforts.

Re:192kbps

[DrHanser]

Of course it would have been better if it was recorded as a VBR recording. Let's also not forget that bit for bit, AAC is arguably better than MP3.

Not all formats are created equal; bitrate is a pisspoor measure of audio quality. This is also not music, this is a sound -- there is a huge difference when encoding audio.

Re:Not really surprising

[Anonymous Coward]

That's not the case here. The great earthquake of 2004 ripped apart the crust of the Earth for approximately 150 km. The fact of the matter is that if all of that energy were concentrated at one point, and released simultaneously, it would have left a crater (the energy of the quake was larger than if all of the world's nuclear weapons were detonated).

It is also unreasonable to believe that 150 km of crust would be rigid in the sense that all points snapped simultaenously. In reality what occured is that it cascaded. One part of the crust slipped which provided the energy for the adjacent layer to slip. From physics we know that the rate of energy propagation due to shear stress is the speed of sound in that material (related to the bulk modulus for the material--which is why craters always form as hemispheres, but that is another story). So the fault kept of slipping at a very fast speed (but not instantly), over an enormous distance which is part of the reason why the sound file is so lengthy. One geophysicist remarked in another article (I think it was on MSNBC) that he could hear the crust being ripped apart. The frightening thing is that this was true.