Relationship between Near-Field and Teleseismic Observations of Seismic Source Parameters
Final rept. 1 Apr 1973-30 Sep 1977
PENNSYLVANIA STATE UNIV STATE COLLEGE DEPT OF GEOSCIENCES
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The following summary outlines the accomplishments under this grant. It was determined 1 There are significant variations in body-wave and surface wave excitation for explosions of comparable magnitude detonated in similar source media and located only a few kilometers apart at NTS Yucca Flats and Pahute Mesa. These observed differences in excitation and energy partitioning imply either a rapidly varying tectonic stress field in the source region andor strongly varying patterns of near-source fracturing. Source- generated P-wave code of two minutes duration or more are observed at NORSAR to vary significantly in strength and character among nearby Yucca and Pahute events, possibly due to short-period surface wave to P-wave scattering 2 that relatively few SRO-type stations can be used to compare source mechanisms for suites of events of varying size in a given source region. For example, foreshocks and aftershocks of the Utah-Idaho border and Oroville, California sequences of 1975, as recorded at the Albuquerque SRO station, have been analyzed and compared in both cases the principal foreshock exhibited the same mechanisms as the main shock, while the aftershocks are more varied in mechanism. For both sequences we were able to match the observed Love and Rayleigh waveforms and spectra as the mechanisms changed. Average path dispersion Hence structure is a useful by-product of the anlaysis.
- Seismic Detection and Detectors