Abstract
The precision of measurement of surface-wave phase velocities at very long periods has reached a point where the exact, rather than asymptotic, form of the spherical harmonics must be considered in order to compute theoretical phase velocities or phase delays. The zeroth-order (i.e. constant) polar phase shift afterBrune et al. (1961) applies only between stations antipodal to each other. Everywhere else a correction for incomplete polar phase shift must be applied even if the waves do not cross a pole between the stations. The correction can exceed one percent of the total phase delay and thus be of the same order as the expected regional anomalies. It depends on the epicentral distance on the signal period and on the focal mechanism; the latter dependence can make the practical application cumbersome. We derive first-order asymptotic formulae for the correction of local phase velocities and total phase travel times of Rayleigh waves.
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Contribution No. 247 of the Institute of Geophysics, Swiss Federal Institute of Technology, Zürich.
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Wielandt, E. First-order asymptotic theory of the polar phase shift of Rayleigh waves. PAGEOPH 118, 1214–1227 (1980). https://doi.org/10.1007/BF01593062
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DOI: https://doi.org/10.1007/BF01593062