BASIC RESEARCH IN CRUSTAL STUDIES
Final rept. 1 Sep 1963-31 Dec 1965
TEXAS INSTRUMENTS INC DALLAS SCIENCE SERVICE DIV
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The work falls into four tasks 1 single-layer models 2 multilayer models 3 models with layer thickness variation and 4 experimental studies using field data. The single-layer studies included theoretical investigation of normal and leaking modes, studies of the practical aspects of frequency-wavenumber analysis and investigation of mode separation by multichannel filtering. Theoretical and analog model investigations for two layers over a half-space showed the difficulty in directly observing an intermediate velocity layer using frequencies of 0.5 cps or less. Analog model investigations of a model having a dipping M-discontinuity showed a wide range of phase velocities for ray events, as predicted. Experimental studies of field data showed the usefulness of velocity filtering as an interpretive aid. Correlation statistics for small events showed that only about 50 percent of the energy arriving between the first arrival and surface waves is predictable. For events at small distance delta 30 km, Rayleigh-mode dispersion curves were measured. These suggested low near-surface velocities extending to a depth of 12-km. It was found that receiving arrays inline with the shot are necessary for adequate dispersion measurements.