MOSAIC STRUCTURE OF THE WAVE FIELDS OF DISTANT EARTHQUAKES

Abstract

The main results are presented of an analysis of the structures of the seismograms. Structure is understood to mean the set of the following factors characteristic of the wave field: number of regular waves, their relative positions on the seismogram, their properties (intensity, shape, frequencies, prominance in the dynamic field and degree of correlation), as well as the seismic background intervening between waves. It is found that there is no unambiguous correlation between the characteristics of the wave field in the horizontal and vertical components. Even when a longitudinal P wave consists of one simple, short 2- or 3-phase pulse, the recordings of the X and Y components show a great diversity of both simple and complex interfering wave fields, which vary along the profile. This mosaic structure of the wave field reflects the block structure of the geological medium and may provide information on it. This is especially important, since in wave propagating in a near-vertical direction the block structure of the medium shows up far more sharply than in refracted waves that for the most part propagate nearly horizontally.