Open AccessP and S Travel Time Anomalies and their Interpretation *
Author(s) -
Hales A. L.,
Doyle H. A.
Publication year - 1967
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1967.tb03139.x
Subject(s) - geology , travel time , seismology , range (aeronautics) , geodesy , interpretation (philosophy) , computer science , materials science , transport engineering , engineering , composite material , programming language
Summary 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 Poisson's ratio between the two regions, and (3) that a model in which the shear modulus, μ, alone varies, the compressibility, k , 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.