A study of blasting recorded in Southern California

As an outcome it is found:

1. For surface paths, or paths of slight depth in the upper (“granitic”—Jeffreys) layer in this region the velocities of the longitudinal and transversal waves are, respectively, 5.5 kilometers per second and 3.21 kilometers per second, very nearly. (With natural shocks, originating below the surface, slightly higher values probably may be expected);

2. A thickness of the upper layer of about 15 kilometers, or of about 25 kilometers, is indicated;

3. No waves have been identified as P_n or S_n with any definiteness;

4. Waves identified as P* and S* appear to be registered in some cases. (The data are consistent with a velocity of 6.2 to 6.3 for longitudinal waves in the second layer);

5. In several cases readings of apparent phase-intervals suggest the existence of a longitudinal wave reflected as a transversal wave at a depth of about 15 kilometers;

6. In one or two cases readings of apparent phase-intervals suggest the possibility of a longitudinal wave reflected as such at a depth of 25 kilometers;

7. At the smaller distances there is some indication of a wave traveling with a velocity of 2.6 kilometers per second.

The need of further data to extend and test these conclusions is apparent.