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U.S. Geological Survey Crustal Studies Technical Letter Number 16

In cooperation with the Defense Advanced Research Projects Agency

Variations in Regional Traveltimes

By J.H. Healy


Thumbnail of and link to report PDF (10.5 MB)Abstract

Precise epicentral location of a seismic event is made difficult by variations in regional traveltimes. A discussion is presented on delays to be expected in the various segments of a generalized travel path of seismic waves.

Traveltime variations caused by changes in crustal structure and velocity introduce a major part of the uncertainty in traveltime at both the seismic source and receiver. Consideration of geologic factors that tend to be related to crustal thickness and mantle velocity may permit an estimate of the amount of delay introduced at the source. Delay at the seismic receiving stations can be determined and corrected for by a study of crustal thickness and a calibration of the velocity structure under the stations.

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Contact Information, Earthquake Science Center, Menlo Park Science Center
U.S. Geological Survey
345 Middlefield Road, MS 977
Menlo Park, California 94025

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Suggested citation:

Healy, J.H., 1964, Variations in regional traveltimes: U.S. Geological Survey Crustal Studies Technical Letter Number 16, 21 p. (Available at




Variations in Traveltime


References Cited

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