Form Approved
REPORT DOCUMENTATION PAGE
OMB No. 0704-0188
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1. AGENCY USE ONLY (Leave blank)
2. REPORT DATE
3. REPORT TYPE AND DATES COVERED
June 1996
4. TITLE AND SUBTITLE
5. FUNDING NUMBERS
Source Location and Tracking Capability of a Small Seismic Array
DA: 4A762784AT42
TA: SS
WU: E02
6. AUTHORS
Mark L. Moran and Donald G. Albert
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
8. PERFORMING ORGANIZATION
REPORT NUMBER
U.S. Army Cold Regions Research and Engineering Laboratory
CRREL Report 96-8
72 Lyme Road
Hanover, N.H. 03755-1290
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
11. SUPPLEMENTARY NOTES
12a. DISTRIBUTION/AVAILABILITY STATEMENT
12b. DISTRIBUTION CODE
Approved for public release; distribution is unlimited.
Available from NTIS, Springfield, Virginia 22161.
13. ABSTRACT (Maximum 200 words)
Recordings of seismic wavefields from various sources were obtained using a small array of vertical-component
geophones under winter conditions at Grayling, Michigan. These data were processed using a frequency-
wavenumber domain Capon minimum variance beamformer to estimate the bearing angle and propagation
velocity of the waves emitted from the source. The cross power matrix was adaptively estimated using a tapered
block-averaging procedure. The wave sources were sledgehammer blows on the ground surface, .45 caliber blank
pistol shots, and an M60 tank moving at 4.5 m s1 along a road near the array. Reliable wavenumber spectra were
obtained for all sources. Processing results for the hammer blows show that the dominant seismic arrival is a
Rayleigh wave traveling at roughly 220 m s1. For the pistol shots, two arrivals corresponding to the airwave (338
m s1) and the air-coupled Rayleigh waves (220 m s1) were observed. The results for these sources were relatively
insensitive to the processing parameters used. For the moving vehicle, the dominant signals observed were
Rayleigh waves (220 m s1). Accurate locations were obtained for this moving source, although the processing
parameters had to be carefully selected, and the choice of frequency parameters affected the accuracy of the
wavenumber results. Maximizing the number of degrees of freedom and the coherence of the frequency estimates
and minimizing the variation of the coherence across adjacent frequency bins provided the most consistently
reliable strategy for obtaining accurate wavenumber estimates for the moving vehicle. The sensitivity of the
wavenumber estimates to the frequency processing parameters seems to be related to the bias in the phase spectra
of the signals and will potentially occur in any bearing estimation method that uses temporal frequncy phase
spectra.
Beam forming
Seismic array processing
14. SUBJECT TERMS
15. NUMBER OF PAGES
44
Capon method
Target location and tracking
Frequency-wavenumber estimation
Unattended ground sensors
16. PRICE CODE
Maximum likelihood method
Wavenumber bias effects
17. SECURITY CLASSIFICATION
18. SECURITY CLASSIFICATION
19. SECURITY CLASSIFICATION
20. LIMITATION OF ABSTRACT
OF REPORT
OF THIS PAGE
OF ABSTRACT
UNCLASSIFIED
UNCLASSIFIED
UNCLASSIFIED
UL
Standard Form 298 (Rev. 2-89)
NSN 7540-01-280-5500
Prescribed by ANSI Std. Z39-18
298-102
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