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Long-period Seismic Noise and Atmospheric Pressure Variations
TELEDYNE GEOTECH GARLAND TX
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Preliminary studies of the long-period seismic noise and the atmospheric pressure fields were made at the Kleer mine near Grand Saline, Texas, during the winter of 1968. The results of the studies indicate that during periods of atmospheric turbulence the vertical and horizontal components of the seismic noise field observed at the surface may increase in total power by as much as 16 and 34 dB within the period range from 20 to 60 seconds. In contrast, long-period systems operated in the mine show little change in power levels regardless of the atmospheric conditions at the surface. The observations are consistent with the hypothesis that the increase observed at the surface is caused by atmospherically-generated deformations of the earth. However, because of questions regarding the surface vaults capability to attenuate pressure changes, the possibility that the noise was caused by vault leakage must be considered an equally likely explanation at the present time. The results indicate that atmospherically-generated seismic noise can seriously degrade the capability of a long-period surface installation to detect surface waves. Because of this finding, further more definitive studies are recommended.
APPROVED FOR PUBLIC RELEASE