Propagation Path Effects for Rayleigh and Love Waves
Semi-annual technical rept.
SOUTHERN METHODIST UNIV DALLAS TX DALLAS GEOPHYSICAL LAB
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Phase-matched filters have been developed for several paths of interest for both Rayleigh and Love waves. The filters are presented in the form of tabled values of apparent group velocity as a function of frequency. Detailed instructions are given as to how the tabled values can be used to construct phase-matched filters and how the filters can be applied to low-level signals which have travelled the same path. Application of the filters provides a time series in which the effects of multipaths have been minimized and on which the signal-to-noise ratio is improved by a factor proportional to the time compression of the signal achieved by the filtering. For a signal bandwidth of 0.1 - 0.015 Hz and an epicentral distance of 30 degrees, the signal-to-noise ratio is about 10 dB better than on the original seismogram. The filtered seismogram can be used for the determination of surface wave magnitude.