The variability of 37 short-period P-wave spectra was studied. Amplitude level is affected by distance and crustal effects. Similarity of the over-all shape of the spectra is attributed to the source. An oscillatory character, present on almost all spectra, is related to the crustal effect. Acting as a mask, the crustal effect prevents quantitative measurements of the attenuation and of the radiation pattern. By an averaging of spectra, the crustal masking can be partly overcome, and an approximation of the spectrum of the pulse incident at the mantle-crust boundary obtained. Selected average spectra suggest that over the frequency range 0.4 to 0.9 cps, very little, if any, differential attenuation takes place. The use of crustal inverse filtering, difficult though it may be, seems required for any quantitative results.

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