NDLI: Processing partially coherent large seismic array for discrimination

Content Provider	IEEE Xplore Digital Library
Author	Lacoss, R.T. Kuster, G.
Copyright Year	1970
Description	Author affiliation: MIT Lincoln Laboratory, Lexington, Massachusetts (Lacoss, R.T.; Kuster, G.)
Abstract	Seismic signals in a band of frequencies near 1.0 Hz. can be detected from underground explosions and earthquakes at distances of several thousand kilometers. A stochastic model has been proposed to characterize observed signal variations within a Large Aperture Seismic Array (LASA). The model assumes that the observed signal spectrum at a seismometer is some average spectrum multiplied by a random gain and phase. Within a subarray (7 km. aperture) the mean value of the modulus squared of the random term is approximated by 1.0 +0.18 f2 where f is frequency in Hz. For sensors drawn from the full LASA (200 km. aperture) the value is 1.0 +2.0 f2. Two alternative methods for extracting spectral information above 1.0 Hz for discrimination between event types are compared. Beamforming spectra are obtained from the Fourier transform of the average received signal. An alternative incoherent processing method, spectraforming, is to calculate the average spectrum from individual seismometers. Both can be corrected for bias. It is demonstrated that although beamforming will give more noise rejection than spectraforming, that the latter can be superior in terms of output signal to noise ratio when input signal variations between sensors are large. Spectraforming may be of significant value for obtaining spectral information in the 1.0 - 3.0 Hz band for events with Richter magnitudes in the range 4.0 - 4.5. This magnitude range is of considerable current interest for the purpose of nuclear test detection and discrimination.
Starting Page	203
Ending Page	203
File Size	624090
Page Count	1
File Format	PDF
DOI	10.1109/SAP.1970.270021
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	1970-12-07
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Apertures Frequency Array signal processing Signal to noise ratio Explosions Earthquakes Stochastic processes Data mining Fourier transforms Testing
Content Type	Text
Resource Type	Article

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