An Assessment of the Use of Strain and Inertial Seismographs to Enhance Seismic Signal to Noise Ratios
TELEDYNE GEOTECH GARLAND TX
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In order to verify compliance with the terms of the proposed comprehensive nuclear test ban treaty, seismic monitoring sites may be located at regional distances from potential test sites. It can be reasonably assumed that some type of signal-to-noise ratio SNR enhancement technique will have to be applied to the raw data collected at these sites in order to detect and identify the source of the relatively weak seismic signals generated by low magnitude earthquakes and underground nuclear explosions. In the past, seismic arrays coupled with simple beamforming data processing methods have been used extensively to enhance short period teleseismic SNRs. Utilization of this technique is based upon the observation that in the frequency bandwidth commonly occupied by teleseismic signals, the signal field generally appears to be much better organized than the ambient earth noise. However, recent studies by Mrazek et al 1979 indicate that the lateral decorrelation of regional signal fields is comparable to that of the earth noise field in commonly shared bandwidths. Under these conditions, the use of horizontally distributed arrays, coupled with simple beamforming techniques is not likely to yield significant improvements in regional SNRs. Thus, there is a need to reassess the use of existing SNR enhancement methods as they pertain to the detection and identification of weak regional seismic signals.