Seismic Observation of Infrasonic Signals
Final rept. 15 Jul 1983-14 Jul 1984
TELEDYNE GEOTECH GARLAND TX
Pagination or Media Count:
A sliding pure-state filter attenuated wind-induced noise recorded by individual elements of a four-element microbarograph array an average of 22 dB. Summation of the processed microbarograms yielded an additional 5 dB attenuation, whereas summation of the unprocessed microbarograms attenuated the noise 6 dB relative to the individual microbarograms. A sliding pure-state filter yielding separate estimates of linearly and elliptically polarized arrivals, applied to the outputs of three-component, long-period inertial seismographs at a site near McKinney, Texas, and at Seismic Research Observatories ANMO, BOCO, and GRFO detected infrasonic signals from five eruptive sequences of E1 Chichon volcano. Application of the pure-state filter improved the signal-to-noise ratio of the seismically detected infrasonic signals an average of 14 dB. A combination of adaptive beam forming and pure- state filtering applied to the outputs of the seven elements of the NORSAR three-component, long-period array marginally detected an infrasonic signal from the largest E1 Chichon eruption.