Amplitude-periodband diagrams and amplitude spectra of teleseismic body waves

The relation between amplitude-periodband (APB) diagrams and Fourier spectra of teleseismic P and S waves was analyzed using displacement-proportional signals derived from magnetic tape records of the feedback-controlled broadband velocigraph operating at the KHC seismic station. Most Fourier spectra and all the APB diagrams of the wave groups investigated exhibit a more or less pronounced maximum and do not correspond to the shape of theoretical far-field spectra for the Brune model. Contrary to Fourier spectra, APB diagrams have an unambiguously defined level and are not influenced by truncation, incorrect zero level and other disturbing effects.