Accession Number:

AD0652219

Title:

P AND S TRAVEL TIME ANOMALIES AND THEIR INTERPRETATION

Descriptive Note:

Corporate Author:

SOUTHWEST CENTER FOR ADVANCED STUDIES DALLAS TX GEOSCIENCES DIV

Personal Author(s):

• Hales, A. L.
• Doyle, H. A.

Report Date:

1967-04-01

Pagination or Media Count:

31.0

Abstract:

Study of the deviations of P and S travel times from the J-B tables at teleseismic distances has shown that there are regional differences in travel time. Both P and S are early in the central and eastern United States, late in the western United States. The differences have a range of about three seconds for P and eight seconds for S. It can be deduced from the relation between the travel time residuals 1 that the change in shear velocity is approximately one and one-quarter times the change in P velocity, 2 that the observations imply a difference in Poissons ratio between the two regions, and 3 that a model in which the shear modulus alone varies, the compressibility remaining sensibly constant, fits the data best. It can be shown also that the differences between the P travel time residuals and the gravity anomalies in the central and western United States are not consistent with the Birch relation between velocity and density.

Descriptors:

• *ANOMALIES
• EARTHQUAKES
• LITHOSPHERE
• POISSON RATIO
• SEISMIC WAVES
• SEISMOGRAPHS
• SEISMOLOGY
• TEMPERATURE

Subject Categories:

• Seismology
• Operations Research

Distribution Statement:

APPROVED FOR PUBLIC RELEASE