Empirical m sub b:M sub s Relations at the Nevada Test Site with Applications to m sub b-Yield Relations.

摘要

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 s:Yield 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.