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Part I. The Radiation of Elastic Waves from a Spherical Cavity in a Half Space. Part II. Precision Determination of Focal Depths and Epicenters of Earthquakes


Cisternas, Armando (1965) Part I. The Radiation of Elastic Waves from a Spherical Cavity in a Half Space. Part II. Precision Determination of Focal Depths and Epicenters of Earthquakes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/K750-5J16.


Part I: The dynamic response of an elastic half space to an explosion in a buried spherical cavity is investigated by two methods. The first is implicit, and the final expressions for the displacements at the free surface are given as a series of spherical wave functions whose coefficients are solutions of an infinite set of linear equations. The second method is based on Schwarz's technique to solve boundary value problems, and leads to an iterative solution, starting with the known expression for the point source in a half space as first term. The iterative series is transformed into a system of two integral equations, and into an equivalent set of linear equations. In this way, a dual interpretation of the physical phenomena is achieved. The systems are treated numerically and the Rayleigh wave part of the displacements is given in the frequency domain. Several comparisons with simpler cases are analyzed to show the effect of the cavity radius-depth ratio on the spectra of the displacements.

Part II: A high speed, large capacity, hypocenter location program has been written for an IBM 7094 computer. Important modifications to the standard method of least squares have been incorporated in it. Among them are a new way to obtain the depth of shocks from the normal equations, and the computation of variable travel times for the local shocks in order to account automatically for crustal variations. The multiregional travel times, largely based upon the investigations of the United States Geological Survey, are confronted with actual traverses to test their validity.

It is shown that several crustal phases provide control enough to obtain good solutions in depth for nuclear explosions, though not all the recording stations are in the region where crustal corrections are considered. The use of the European travel times, to locate the French nuclear explosion of May 1962 in the Sahara, proved to be more adequate than previous work.

A simpler program, with manual crustal corrections, is used to process the Kern County series of aftershocks, and a clearer picture of tectonic mechanism of the White Wolf fault is obtained.

Shocks in the California region are processed automatically and statistical frequency-depth and energy depth curves are discussed in relation to the tectonics of the area.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Geophysics and Mathematics)
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geophysics
Minor Option:Mathematics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Press, Frank
Thesis Committee:
  • Unknown, Unknown
Defense Date:28 May 1964
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)AF-49(638)-1337
Record Number:CaltechTHESIS:03202015-145559091
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8799
Deposited By: Bianca Rios
Deposited On:20 Mar 2015 22:48
Last Modified:10 Feb 2024 00:46

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