Empirical m sub b:M sub s Relations at the Nevada Test Site with Applications to m sub b-Yield Relations
TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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Measurements have been made of first-motion amplitude and of the period and amplitude of the second peak-to-trough excursion termed the c phase for short-period vertical P-wave signals from approximately 60 Nevada Test Site NTS explosions. They were recorded at the Long-Range Seismic Measurement LSRM and Seismic Data Collection System SDCS stations in Houlton, Maine HNME, and Red Lake, Ontario RKON. Almost all events selected were detonated in saturated tuff or rhyolite. Care was taken to avoid gross errors and to minimize effects of apparent minor perturbations of the waveforms, which cause zero-crossings, the so-called false cycles. The c-phase data are plotted as a function of M sub s and are interpreted to show amplitude variations of several tenths in magnitude with respect to an M sub sYield curve with slope of 1.0. These amplitude variations are due independently to 1 the influence of yield on corner frequency 2 interference with the pP phase and 3 geographic location within NTS. Several tenths of a second variation in period can also be traced to the above 3 causes. The variation with geographic location may be due to variation of the upper 2 km of structure at NTS or to multipathing and ray divergency because of more deeply seated structures.