08-09-2009, 11:14 PM
Posted by mayank at 6:13 AM
Sunday, August 9, 2009
You canââ¬â¢t hear it, but the Earth is constantly humming. And some parts of the world sing louder than others.
After discovering the mysterious low-frequency buzz in 1998, scientists figured out that the Earthââ¬â¢s hum is caused not by earthquakes or atmospheric turbulence, but by ocean waves colliding with the seafloor. Now, researchers have pinpointed the source of the Earthââ¬â¢s ââ¬Åbackground noise,ââ¬Â and it looks like itââ¬â¢s coming primarily from the Pacific coast of North America.
When two waves of opposite direction but similar frequency collide, they create a special kind of pressure wave that carries energy to the ocean bottom. As these waves pound against the sea floor, they generate a constant vibration with a frequency of about 10 millihertz, much too low for humans to hear but easily detectable with seismometers. By comparing the intensity of the hum with the height of waves around the world, scientists can track where the buzz is coming from.
Previous studies suggested that waves from both shallow continental shelves and the deep ocean contribute to the Earthââ¬â¢s hum, but new data indicates otherwise. Based on measurements from a seismic observatory called the USArray EarthScope, most of the hum appears to originate from the Pacific coast of North America, with a smaller contribution from the west coast of Europe. Waves from the deep ocean donââ¬â¢t seem to make much hum at all.
http://mytechnologyworld9.blogspot.com/2...arths.html
Sunday, August 9, 2009
You canââ¬â¢t hear it, but the Earth is constantly humming. And some parts of the world sing louder than others.
After discovering the mysterious low-frequency buzz in 1998, scientists figured out that the Earthââ¬â¢s hum is caused not by earthquakes or atmospheric turbulence, but by ocean waves colliding with the seafloor. Now, researchers have pinpointed the source of the Earthââ¬â¢s ââ¬Åbackground noise,ââ¬Â and it looks like itââ¬â¢s coming primarily from the Pacific coast of North America.
When two waves of opposite direction but similar frequency collide, they create a special kind of pressure wave that carries energy to the ocean bottom. As these waves pound against the sea floor, they generate a constant vibration with a frequency of about 10 millihertz, much too low for humans to hear but easily detectable with seismometers. By comparing the intensity of the hum with the height of waves around the world, scientists can track where the buzz is coming from.
Previous studies suggested that waves from both shallow continental shelves and the deep ocean contribute to the Earthââ¬â¢s hum, but new data indicates otherwise. Based on measurements from a seismic observatory called the USArray EarthScope, most of the hum appears to originate from the Pacific coast of North America, with a smaller contribution from the west coast of Europe. Waves from the deep ocean donââ¬â¢t seem to make much hum at all.
http://mytechnologyworld9.blogspot.com/2...arths.html