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U.S. Department of Energy
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Modeling teleseismic SV waves from underground explosions with tectonic release: results for Southern Novaya Zemlya

Technical Report ·
OSTI ID:6872911
Detailed forward modeling of long-period shear waves for 2 large underground explosions at the Southern Novaya Zemlya test site indicates that the appropriate equivalent double-couple orientation for the tectonic release radiation is vertical strike-slip. Previous studies of observed teleseismic SH waveforms and SV amplitudes for the 27 Oct 1973 and 2 Nov 1974 events using geometric theory could not distinguish between vertical strike-slip and 45 deg-dipping thrust geometries. Either mechanism can match the observed four-lobed SH radiation pattern, and the two-lobed SV amplitude pattern can be produced by interference with an appropriate-size explosion pS signal. However, the complexity of the observed SV waveforms arising from Sp conversions near the receiver, diffracted Sp, and shear-coupled PL phases is not accounted for in the ray-theory synthetics. Incorporating more-realistic Green's functions using Baag and Langston's WKBJ spectral method allows more-complete modeling of the SV signals. Due to differences in frequency content between the explosion and double-couple SV waveforms, constructive interference occurs more efficiently than destructive interference when the two signals are linearly superimposed. As a result, using tectonic-release moments determined from the SH waves and the optimum F factors required to match the SV amplitude patterns, the waveforms produced by the strike-slip and thrust orientations differ substantially at some azimuths.
Research Organization:
Michigan Univ., Ann Arbor (USA). Dept. of Geological Sciences
OSTI ID:
6872911
Report Number(s):
AD-A-199243/7/XAB
Country of Publication:
United States
Language:
English