Reflected and minor phases in records of near-by earthquakes in southern California

Abstract

The present paper is a direct continuation of a recent paper (Gutenberg, 1944a) in which the author has discussed travel times of the major P and S phases recorded at near-by stations for fifty southern California earthquakes. To facilitate the present investigation of phases complicated by refraction and reflection, thorough consideration was given to the partition of energy into the various reflected and refracted waves at discontinuities and to the ratio of ground displacements to the incident amplitudes at the surface of the earth (Gutenberg, 1944b). This seems desirable since the number of theoretically possible phases to be expected is very large, considering the four layers in the earth's crust; consequently, any calculated curve can be "verified" by using small impulses to be found on most seismograms. Therefore, clearly recognizable phases should be used in such investigations, and only calculated travel times for waves with amplitudes theoretically large enough to be conspicuous.