Bulletin of the Seismological Society of America
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Bulletin of the Seismological Society of America; July 1955; v. 45; no. 3; p. 219-244
© 1955 Seismological Society of America
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by DE BREMAECKER, J. CL.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

Use of amplitudes, Part I: Pn from 3° to 23°*

J. CL. DE BREMAECKER

INSTITUT POUR LA RECHERCHE SCIENTIFIQUE EN AFRIQUE CENTRALE (I.R.S.A.C.), BUKAVU, Belgian Congo

Abstract

Ten seisms with epicentral distances between 3° and 23° are studied.

Gutenberg's method to find the variation of Pn amplitudes with distance is applied. It results in observations too scattered to permit any conclusion.

The second method uses a combination of seisms, each observed in a limited range. A minimum is found around 7° and a maximum around Formula.

The essence of the proposed theoretical explanation is the coexistence of "Muskat's rays"{dagger} (refracted rays) and of "direct rays" and the existence of "Muskat's rays" along the boundary of two media, in one of which the velocity increases with depth. The results are well explained by comparing the amplitudes due to these two rays.

The following structure of the earth's crust best explains the results: speed above the Mohorovicic discontinuity, 6.3 km/sec.; speed immediately below it, 8.1 km/sec.; speed at 80 km. depth, between 8.10 km/sec. and 8.128 km/sec.; around 80 km., decrease in the rate of increase of speed with depth, or decrease of speed with depth < 0.001293 km/sec/km.; depth of the discontinuity, 35 km.; {sigma}1 = {sigma}2 = 0.25; density ratio = 1.103.

Footnotes

* Manuscript received for publication December 11, 1953.

{dagger} Note added in proof: Since the time of this writing, various papers have been published by Macelwane's students using the term "head-wave" for what is here called "Muskat's rays." As the former term is not ambiguous and is now in current use, it should be preferred.




This article has been cited by other articles:


Home page
 Bulletin of the Seismological Society of AmericaHome page
G. A. MCMECHAN and W. G. WORKMAN
P-wave amplitudes and magnitudes between 10{degrees} and 35{degrees}
Bulletin of the Seismological Society of America, December 1, 1974; 64(6): 1887 - 1899.
[Abstract] [PDF]

Home page
 Bulletin of the Seismological Society of AmericaHome page
K. L. KAILA
Decay rate of P-wave amplitudes from nuclear explosions and the magnitude relations in the epicentral distance range 1{degrees} to 98{degrees}
Bulletin of the Seismological Society of America, April 1, 1970; 60(2): 447 - 460.
[Abstract] [PDF]

Home page
 Bulletin of the Seismological Society of AmericaHome page
J. JORDAN, R. BLACK, and C. C. BATES
Patterns of maximum amplitudes of Pn and P waves over regional and continental areas
Bulletin of the Seismological Society of America, August 1, 1965; 55(4): 693 - 720.
[Abstract] [PDF]

Home page
 Bulletin of the Seismological Society of AmericaHome page
C. ROMNEY
Seismic waves from the Dixie Valley-Fairview Peak earthquakes
Bulletin of the Seismological Society of America, October 1, 1957; 47(4): 301 - 319.
[Abstract] [PDF]

Home page
 Bulletin of the Seismological Society of AmericaHome page
J. CL. DE BREMAECKER
Use of amplitudes: Part II, focal depths
Bulletin of the Seismological Society of America, October 1, 1955; 45(4): 279 - 284.
[Abstract] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1955 by the Seismological Society of America.