Progress Report on Recent Improvements in the Analysis of Surface Wave Observations

Abstract

Several new digital techniques have been developed to improve the quality of information which may be extracted from surface wave recordings. The main topics covered by this progress report are(1) Moving window analysis and the multiple filter technique which are automatic digital processes of considerable utility in the measurement of multi-mode dispersion.(2) Combined multi-component analytic techniques for the identification and separation of wave types.(3) Time-variable filtration in the frequency domain, based upon the fast Fourier transform. This permits the separation of a mode of interest from a multi-mode recording, with insignificant disturbance of the desired phase information.(4) Cross-correlation for inter-station phase and group velocity measurements.