Array analysis of regional Pn and Pg wavefields from the Nevada test site

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1991

OSTI ID:6147165

Leonard, M A

Small-aperture high-frequency seismic arrays with dimensions of a few kilometers or less, can improve our ability to seismically monitor compliance with a low-yield Threshold Test Ban Treaty. The characteristics and effectiveness of array processing of the regional Pn and Pg wavefields generated by underground nuclear explosions at the Nevada Test Site are examined. Waveform data from the explosion HARDIN (m[sub b] = 5.5) is recorded at a temporary 12-element, 3- component, 1.5 km-aperture array sited in northern Nevada. The explosions VILLE (m[sub b] = 4.4) and SALUT (m[sub b] = 5.5) are recorded at two arrays sited in the Mojave desert, one a 96-element vertical-component 7 km-aperture array and the other a 155-element vertical-component 4 km-aperture array. Within the aperture of each array spectral amplitudes vary significantly among sensors. There are significant differences in low-frequency spectral amplitudes between array sites but become nearly identical beyond about 6 Hz. Seismic source properties and the partitioning of energy between Pn and Pg are examined. Frequency-wavenumber analysis at the 12-element array is used to estimate signal gain, phase velocity, and source azimuth. Frequency-dependent biases are found in velocity and azimuth of the coherent Pn and Pg arrivals. Incoherent scattering occurs after a little over one second into the Pn wavefield and throughout the Pg wavefield. Lack of signal correlation on horizontal components severely limits the utility of 3-component processing. Signal correlation is examined in terms of spatial coherence estimates. The coherence varies but in all cases the coherence of Pn is greater than that for Pg. The coherence estimates are used to construct spatially-continuous frequency-dependent models of cross-spectra, used to stimulate array processing performance for arbitrary sensor configurations. Simulations are used to rank the three locations in terms of their potential as regional monitoring array sites.

• Research Organization: California Univ., Berkeley, CA (United States)
• OSTI ID: 6147165
• Country of Publication: United States
• Language: English

Related Subjects

350300 -- Arms Control-- Verification-- (1987-)
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
450200* -- Military Technology
Weaponry
& National Defense-- Nuclear Explosions & Explosives
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION
AZIMUTH
COMPLIANCE
EXPLOSIONS
INCOHERENT SCATTERING
MEASURING INSTRUMENTS
NATIONAL ORGANIZATIONS
NEVADA TEST SITE
NUCLEAR EXPLOSIONS
PHASE VELOCITY
SCATTERING
SEISMIC ARRAYS
TREATIES
UNDERGROUND EXPLOSIONS
US DOE
US ORGANIZATIONS
VELOCITY
VERIFICATION