Analysis of near-source contributions to early P-wave coda for underground explosions. 1. Wave form complexity
A data set of more than 1600 teleseismic short-period P waves from 46 nuclear explosions is analyzed to establish near-source contributions to the first 15 sec of the P signals. The near-source components are isolated by event-to-event comparisons of first-cycle magnitudes, RMS amplitudes in the first 5 and next 10 sec of the wave forms, and energy temporal centroid measurements. Events from the Nevada, Amchitka, and Novaya Zemlya test sites are analyzed separately to characterize overall source-region variations. Event-averaged waveform complexity variations between explosions within a given site are tested for dependence on source strength, burial depth, location within the site, and tectonic release. Azimuthal patterns of the individual event complexity anomalies are used to discriminate between possible near-source influences. For events at Pahute Mesa, a strong azimuthal amplitude pattern in both the direct P waves and the P coda for all of the events is produced principally by deep mantle variations. Defocusing by a high-velocity anomaly in the crust and uppermost mantle beneath the site has a stronger effect on the direct P signals than on the early P coda, resulting in a systematic, spatially varying relative pattern.
- Research Organization:
- Michigan Univ., Ann Arbor (USA). Dept. of Geological Sciences
- OSTI ID:
- 6520045
- Report Number(s):
- AD-A-200017/2/XAB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
450202* -- Explosions & Explosives-- Nuclear-- Weaponry-- (-1989)
58 GEOSCIENCES
580201 -- Geophysics-- Seismology & Tectonics-- (1980-1989)
ALEUTIAN ISLANDS
AZIMUTH
DEPTH
DIMENSIONS
EARTH CRUST
EARTH MANTLE
EXPLOSIONS
FEDERAL REGION IX
ISLANDS
NEVADA
NORTH AMERICA
NUCLEAR EXPLOSIONS
SEISMIC P WAVES
SEISMIC WAVES
TECTONICS
TEST FACILITIES
UNDERGROUND EXPLOSIONS
USA
WAVE FORMS