Some aspects of band-pass filtering of surface waves

Abstract

abstract Narrow band-pass filtering of multi-mode surface-wave signals can be used to extract information concerning the group velocities and spectral amplitudes of each mode. A detailed examination of narrow band-pass filtering shows the effect of epicentral distance and the shape of the group-velocity curve upon the filtered signal. With this knowledge, the filtered signal can be used to make accurate estimates of the spectral amplitudes of each mode. A rectangular and a Gaussian filter are considered in detail. A numerical example is provided to indicate the values and limitations of the technique for determining the spectral amplitudes of each mode.