J. Louie - The Sound of Seismic

The Sound of Seismic

John N. Louie, 21 August 2008

J. Louie's Research and Teaching -- Nevada Seismological Lab

The links below present examples of earth sounds recorded by seismometers. Seismometers are different from microphones and hydrophones in that they are sensitive to lower frequencies than people can hear, and they record a single direction of ground vibration.

These sounds, as well as videos illustrating seismic wave propagation, are being released as Podcast episodes for Apple iTunes and iPod listeners. Subscribe to http://www.seismo.unr.edu/sounds/sound-of-seismic.xml . New episodes will be posted as we record data and make analyses.

The sounds in the pages below are presented as MP3 files, usually after speeding them up by factors of 10 to 50. Animations of wave propagation are usually sped up by a factor of 10, and are presented as M4V iPod MPEG-4 video files. Both formats will play on all popular multimedia players.

Follow this link to obtain Louie's JRG software, that can translate seismograms to audio files.

All of the sound, video, and graphic files presented in the pages below have been authored by John N. Louie and are in the public domain, so are free for any use. All text is copyright © 2001-2008 John N. Louie.

Example Sounds:

Annotated video of scenario shaking from the West Reno-Mogul and Wells, Nevada earthquakes

Geol 455 class project: Earthquake scenarios affecting Nevada urban areas

An earthquake sequence in New Zealand

Singing sands at Sand Mountain, Nevada

Simulated earthquake in southern Nevada

Gold mine blast in northern Nevada

Microtremor at the Reno/Tahoe Airport

Microtremor at Mud Island, Memphis

A 3-d seismic survey record

Each example also includes a visual plot of the seismogram data, or maps of wave propagation, as color images. Wave-propagation maps are presented as downloadable, podcast video animations. In the seismogram plots, the time progression of sound amplitude is presented as strips, with time increasing either from left to right, or from top to bottom. The time axis is labeled with the original true time, not the sped-up time. Each plot image links to a high-resolution PDF plot.

The topmost or leftmost seismogram strip plays into the left ear, and the next adjacent strip plays into the right ear. Most of the seismograms continue to alternate into the left and right channels in this manner.

The color of the image is keyed to the sound amplitude. The amplitude usually represents the vertical ground particle velocity, and not the total sonic pressure. Red colors show strong upward particle velocity, often associated with increasing sonic pressure in the ground. Blue colors show strong downward particle velocity, often associated with decreasing sonic pressure. White indicates little or no vertical particle velocity, and little or no sound output. But elastic waves in the ground may still have substantial amplitude, even when there is no vertical particle velocity, sonic pressure, or sound heard from these files. The amplitude would be in the transverse waves not seen in the vertical vibration direction.

Andy Michael and Dennis Ross created the Listening to Earthquakes pages at the US Geological Survey, with many additional examples.

Dr. Florian Dombois has a well-referenced set of presentations on-line for Auditory Seismology.

J. Louie's Research and Teaching -- Nevada Seismological Lab