(1.1 Mb) Recording from two seismometers 100 feet apart
Louie's professional seismic recording equipment was in repair at the time, so he recorded two geophones wired into the sound input of his laptop (as shown for about 1 second in Burning Sands). The left channel of the recording below is from a horizontal geophone (sensitive to horizontal particle motion) at the base of the dune's slip face. The right channel is from a vertical geophone at the dune crest. This recording in not speeded up, and you can hear the crew conversing, through the geophones.
The recording begins with Dr. Nori plowing sand down the slip face near the crest (strong in the right ear), and proceeds as he sleds down the face past the lower geophone 100 feet away (strong in the left ear). Starting at about 45 seconds into the recording you will hear the booming strongly. It is a strong resonance at about 70 Hz frequency. Good headphones or a subwoofer are necessary to hear this low frequency well.
The plot below shows graphically just a segment of the strong booming. Time increases toward the right in this plot:This recording is also available as a Podcast episode for Apple iTunes and iPod listeners. Subscribe to http://crack.seismo.unr.edu/sounds/sound-of-seismic.xml. A new episode will be posted each month.
