Earth Noise in the 20- to 100-Second Period Range
TELEDYNE GEOTECH GARLAND TX
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Experiments to investigate the sources of seismic noise in the period range of 20 to 100 seconds have been conducted at three observatories, Grand Saline and McKinney, Texas and Pinedale, Wyoming. For surface seismographs the main contributor to the noise is quasi-static earth motion caused by wind- generated pressure variations. These pressure variations were recorded by microbarographs and shown to be linearly related to the noise recorded by seismographs during windy periods. During windless periods frequency-wave number analysis shows that infrasonic waves contribute to the noise recorded by long- period seismometers. Attenuation of the effect of short wavelength wind- generated pressure variations can be accomplished by two means burial of the seismometer below the surface and optimum filtering techniques. The depth of burial required to eliminate the wind-generated noise is approximately in agreement with theory.
- Seismic Detection and Detectors