Posted on 07/23/2005 4:03:54 AM PDT by bd476
Sound from last December's huge tsunami-causing earthquake was picked up by underwater microphones designed to listen for nuclear explosions.
Scientists this week released an audio file of the frighteningly long-lasting cracks and splits along the Sumatra-Andaman Fault in the Indian Ocean.
The spine-tingling hiss and rumble is an eerie reminder of the devastation and death that is still being tallied in the largest natural disaster in modern times.
At least 200,000 people are thought to have died as a result of the magnitude 9.3 earthquake, the tsunami, and the lack of food, drinkable water and medical supplies that followed.
The audio recording of the quake starts out silent. A low hiss begins and the intensity builds gradually to a rumbling crescendo. Then it tails off but, frighteningly, builds again in waves as Earth continues to tremble.
The audio file [here] is sped up 10 times to make it easier to hear. As it was recorded, the sound was at the lower threshold of human hearing, but it could have been noted by someone paying attention.
"If you were diving even hundreds of miles away you could hear this," said study leader Maya Tolstoy of Columbia University's Lamont-Doherty Earth Observatory. "You would hear it as sort of a 'boom.'"
Future help
An analysis of the recording suggest a new way to monitor earthquakes in near real-time, providing critical information about an earthquake's intensity and potential hazard that could supplement seismograph data, which typically requires hours and even days to properly analyze.
"We were able to constrain some details such as the speed and duration of the rupture more accurately than traditional seismic methods," Tolstoy said. "Moreover, we found the earthquake happened in two distinct phases, with faster rupture to the south and slower to the north, almost as if there were two back-to-back events."
Tolstoy told LiveScience that the recorded sounds raced from the rupture more quickly than the tsunami wave. The entire quake's sounds took about 45 minutes to reach the hydrophone. Were a system set up to use such data, analysis might be done in about 15 minutes, Tolstoy said.
The tsunami took hours to reach some locations.
An analysis of the data is detailed in the July/August edition of the journal Seismological Research Letters.
Sound travels
It is not surprising the sounds were picked up.
An earthquake releases energy of varying types. Its seismic waves -- those that shake the ground -- are technically just a variation on sound waves. And sound travels well in water. Whales can hear each other call from more than 1,000 miles away.
Tolstoy said people at sea have heard the rumblings of distant volcanoes when the sound hits the hull of a ship.
And this was no small earthquake. It ruptured the planet along 750 miles (1,200 kilometers) of fault. Scientists estimate the Indian plate slipped 33-50 feet (10 to 15 meters) under the Burma microplate. The fault shook for at least eight minutes. A typical large earthquake lasts 30 seconds or so.
Earth's very gravity balance was altered and the North Pole shifted by an inch.
The recorded data was provided in March to scientists by the International Monitoring System of the Comprehensive Nuclear Test Ban Treaty. Tolstoy and her colleague, DelWayne Bohnenstiehl, converted the data to make the new audio file.
Tolstoy hopes that in the future scientists will gain easier and earlier access to such data.
"There is an opportunity here to make a contribution to international disaster monitoring, as well as help us better understand earthquakes and tsunamis and potentially mitigate these events in the future." she said. "It makes sense to let others listen in."
The sound file is here.
A spectrogram of the data shows energy released, with red being the most. A peak in energy is seen about 300 seconds into the event. Credit: Lamont-Doherty Earth Observatory
I saved it, and I have it on my machine, ran it through my anti-virus three times before even playing it.
I even slowed the play speed down using the Nullsoft Signal Processing Studio DSP plugin, and Justins Simple Pitch and Tempo script to check it out.
When it is slowed down to half speed, the sound is quite interesting.
It isn't as noticably loud, but it is a long rending rumble.
And they said they speed the recording up a bit.
I'm not a signal analyst, but the quake had neat characteristics since it ruptured 750 miles of faultline.
(Or so I read. What you're hearing in the recording if true is 750 miles worth of faultline moving.)
LOL! Glad you liked it. :-)
It's incredible to imagine the force of one of Earth's plates starting to slide under another of Earth's plates.
Good that you checked it out before saving it. I wonder what it would look like on a scope.
Oh I hope not Randall. I doubt they listen to anything that good.
Yes.
On the oscilloscope, the sine wave is weird, irregular.
Spectrum analyzer shows it being all roughly in the 60 hz and 170 hz area.
On a voiceprint, it has a speckled salmon appearance, but only when you drop the voiceprint from 500 bands down to 40.
I'm thinking on swapping the voiceprint colors to contrasting colors to see what that does, see if there is anything odd to see.
There is a weird line in the voiceprint, but that could be an artifact of mp3 compression.
I have seen such in my music.
Just redid the osciloscope eyeballing using a bigger screen resolution.
The irregular wave form described earlier was an artifact of the scope size.
The scope does this neat illusion of five wave forms superimposed on each other.
(Refresh rate of scope 80 frames per second)
All low frequency, and rather uniform.
I can have fun with this . . .
Uh oh.
Now I'm curious.
And also envisioning metamucil commercials for the sumatran fault..
BTTT
Check this out!
Played it for my hound dog. No reaction.
Now if it chirped like a squirrel...
"If you play it backwards, you hear Satan saying, "___________________". <--- (your joke here)"
'I never had sexual relations with that woman....'
Right. We are quite "puny" and insignificant next to the power of nature.
Yeah, I was there with about 4,000 Marines in 29 Palms, 8 miles from epicenter.. Struck at dawn.
It was like standing on a huge speaker; the sound came from everywhere as the earth groaned!
Incredibly loud.
Unfortunately a small girl was killed, but she was the only casualty as I can recall.
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