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; August 1996; v. 86; no. 4; p. 972-980
© 1996 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 Julian, B. R.
Right arrow Articles by Foulger, G. R.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

Earthquake mechanisms from linear-programming inversion of seismic-wave amplitude ratios

Bruce R. Julian and G. R. Foulger

U.S. Geological Survey, 345 Middlefield Rd. MS977, Menlo Park, California 94025
Department of Geological Sciences University of Durham, Durham DH1 3LE, U.K.

Abstract

The amplitudes of radiated seismic waves contain far more information about earthquake source mechanisms than do first-motion polarities, but amplitudes are severely distorted by the effects of heterogeneity in the Earth. This distortion can be reduced greatly by using the ratios of amplitudes of appropriately chosen seismic phases, rather than simple amplitudes, but existing methods for inverting amplitude ratios are severely nonlinear and require computationally intensive searching methods to ensure that solutions are globally optimal. Searching methods are particularly costly if general (moment tensor) mechanisms are allowed. Efficient linear-programming methods, which do not suffer from these problems, have previously been applied to inverting polarities and wave amplitudes. We extend these methods to amplitude ratios, in which formulation on inequality constraint for an amplitude ratio takes the same mathematical form as a polarity observation. Three-component digital data for an earthquake at the Hengill-Grensdalur geothermal area in southwestern Iceland illustrate the power of the method. Polarities of P, SH, and SV waves, unusually well distributed on the focal sphere, cannot distinguish between diverse mechanisms, including a double couple. Amplitude ratios, on the other hand, clearly rule out the double-couple solution and require a large explosive isotropic component.




This article has been cited by other articles:


Home page
 Bulletin of the Seismological Society of AmericaHome page
Y. Tan and D. Helmberger
A New Method for Determining Small Earthquake Source Parameters Using Short-Period P Waves
Bulletin of the Seismological Society of America, August 1, 2007; 97(4): 1176 - 1195.
[Abstract] [Full Text] [PDF]

Home page
 Bulletin of the Seismological Society of AmericaHome page
D. Kilb and J. L. Hardebeck
Fault Parameter Constraints Using Relocated Earthquakes: A Validation of First-Motion Focal-Mechanism Data
Bulletin of the Seismological Society of America, June 1, 2006; 96(3): 1140 - 1158.
[Abstract] [Full Text] [PDF]

Home page
 Bulletin of the Seismological Society of AmericaHome page
Using S/P Amplitude Ratios to Constrain the Focal Mechanisms of Small Earthquakes
Bulletin of the Seismological Society of America, December 1, 2003; 93(6): 2434 - 2444.


Home page
 Bulletin of the Seismological Society of AmericaHome page
A. Nakamura, S. Horiuchi, and A. Hasegawa
Joint focal mechanism determination with source-region station corrections using short-period body-wave amplitude data
Bulletin of the Seismological Society of America, April 1, 1999; 89(2): 373 - 383.
[Abstract] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1996 by the Seismological Society of America.