EARTH
Using a new technique, researchers have boosted seismic waves (top) from the 2011 Tohoku earthquake to frequencies (bottom) within the audible range for humans. SOURCE/Georgia Institute of Technology
The sounds we associate with earthquakes tend to be those induced aboveground. Low-pitched rumbles, rattling windows and car alarms might be heard during small temblors, while more terrifying sounds like the crumbling of concrete and the cacophony of people trying to reach safety sometimes accompany large earthquakes. But what does an earthquake itself sound like, as rock grinds against rock in a rupturing fault and large amounts of energy are released? Thanks to some recent efforts, we may be starting to get an idea.
In truth, it is difficult to know what earthquakes underground sound like because typical seismic waves have frequencies below the audible range for humans, which is between 20 and 20,000 Hertz. Now, however, a group of researchers has given voice to one seismic monster: the March 11, 2011, magnitude-9.0 Tohoku earthquake that rocked Japan and was detected on seismometers worldwide.
By converting seismic data from instruments around the planet to sound files and then playing the recordings back at faster-than-real-time speeds, the researchers boosted the seismic frequencies into the audible range. The technique also condenses the signals so that processes that occurred over several minutes or hours can be heard on much shorter timescales. Depending on where the seismometers that recorded a particular dataset were located, the resulting sounds of the main shock and the aftershocks resemble everything from booming explosions to distant thunderclaps and gentle rainfall to the sound of furniture being rolled across a hardwood floor.
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