Study of Adaptive Beamforming Algorithms for Low Magnitude Seismic P- Wave Detection
TEXAS INSTRUMENTS INC DALLAS EQUIPMENT GROUP
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A linear adaptive algorithm was developed for array beamforming purposes. The design goal for the algorithm was to minimize the squared filter output subject to the constraint which allows energy propagating from the array steering direction to pass without being distorted. The adaptive filter coefficients were designed as time-verying filters applied to each channel subject to the above constraints. The adaptation rate was inversely varied with filter output and total input channel power. Performance of the algorithm was studied by using recorded short-period array data from the Korean Seismic Research Station. To demonstrate adaptive beamforming, a high amplitude signal from Kamchatka, a medium amplitude signal from eastern Kazakh, and a number of low amplitude signals from central Eurasia were processed. Results of signal-to- noise ratio gain relative to a conventional beamformer among the events tested were consistent and were in the range of 4.5 to 6.5 dB in the wide passband. Much better signal-to-noise ratio improvement was obtained in a low frequency passband.
- Seismic Detection and Detectors