Multichannel Deconvolution of P Waves at Seismic Arrays and Three Component Stations
Annual rept. 1 Oct 1985-1 Oct 1986
TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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The results of a new multichannel method, applied to array recordings and three component station networks for teleseismic P waves, are presented and interpreted in terms of possible surface reflections and other arrivals from the Nevada Test Site NTS, Novaya Zemlya, and Eastern Kazakh Test Site EKTS nuclear explosions. The deconvolution method utilizes the well known fact that P wave spectra can be decomposed into source and receiver spectral factors. The source functions obtained in the deconvolution process provide a better picture of the nature of explosion source time functions, and in particular of the presence or lack of secondary arrivals following the P wave such as pP or spall. The presence of such secondary arrivals and their effects on the first cycle of the P wave are very important in yield estimation. For most events at the eastern part of EKTS the source time functions appear to contain a pP arrival but they also show later, unexplained arrivals and other complexities. At other test sites often there are no clearly identifiable pP phases in the deconvolved traces. Joint deconvolution of central EKTS data using all AWRE arrays indicated strong azimuthal asymmetries in the body wave radiation. Deconvolutions of NTS events were considerably degraded by the limited signal bandwidth due to strong mantle attenuation under this test site. The site functions are also complex in most cases. Site and source effects contribute about equally to the energy observed in the P codas of the events analyzed.
- Seismic Detection and Detectors