CaltechAUTHORS
  A Caltech Library Service

Global Q estimates from antipodal Rayleigh waves

Chael, Eric P. and Anderson, Don L. (1982) Global Q estimates from antipodal Rayleigh waves. Journal of Geophysical Research B, 87 (B4). pp. 2840-2850. ISSN 0148-0227. http://resolver.caltech.edu/CaltechAUTHORS:20140513-150602555

[img]
Preview
PDF - Published Version
See Usage Policy.

807Kb

Use this Persistent URL to link to this item: http://resolver.caltech.edu/CaltechAUTHORS:20140513-150602555

Abstract

Global average estimates of the group velocity and attenuation of long-period (120–300 s) Rayleigh waves were made using seismograms from the epicenter's antipode (Δ≃180°). Focusing at the antipode produced amplified arrivals with favorable signal-to-noise ratios. The high-quality data yielded very stable attenuation values, with excellent agreement between the results from successive Rayleigh arrivals for a single event and between the results for two different events. Lateral heterogeneities in earth structure can cause systematic biasing of attenuation measurements based on antipodal records. The initial, uncorrected results therefore provide a lower bound estimate of global Q. An ellipsoidal perturbation in shape was used to simulate the effects of lateral velocity heterogeneities on Rayleigh wave propagation. Using the agreement of repeated attenuation measurements as a constraint, we estimated both the bias in those measurements and the splitting widths of the Rayleigh modes. At a period of 200 s, the estimated splitting width is 0.30% this agrees closely with calculations by Luh (1974) for an earth model with different continental and oceanic velocity profiles. The estimated bias varied from 30% to zero over the 120- to 260-s band. After correcting for bias, the antipodal Q values range from 108 at 120 s to 188 at 260 s. These Q are within the range of previous measurements but are lower than the mean values from typical great circle studies, implying that the globally averaged upper mantle is slightly more attenuative than has been generally recognized.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://onlinelibrary.wiley.com/doi/10.1029/JB087iB04p02840/abstractPublisherArticle
http://dx.doi.org/10.1029/JB087iB04p02840DOIArticle
Additional Information:© 1982 American Geophysical Union. Received June 12, 1981; revised January 22, 1982; accepted January 29, 1982. Paper number 2B0176. We are indebted to Jose Rial, whose work with the antipodal body waves of the PTO record directly inspired this study. He introduced E.P.C. to the project and offered many valuable suggestions. We would also like to thank Tony Dahlen and Adam Dziewonski for pointing out the need to consider the bias in antipodal Q measurements. Ray Buland kindly provided mode tapes for model 1066A. Hiroo Kanamori and Jeff Given reviewed the manuscript and suggested improvements. We thank Adam Dziewonski and Joseph Steim for a timely preprint which lent support to our results. This research was supported by the National Science Foundation under contract EAR77-14675. E. P. C. was supported in part by a National Science Foundation graduate fellowship. Contribution 3644, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125.
Funders:
Funding AgencyGrant Number
NSF EAR77-14675
NSF Graduate FellowshipUNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences3644
Record Number:CaltechAUTHORS:20140513-150602555
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140513-150602555
Official Citation:Chael, E. P., and D. L. Anderson (1982), Global Q estimates from antipodal Rayleigh waves, J. Geophys. Res., 87(B4), 2840–2850, doi:10.1029/JB087iB04p02840.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45728
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:13 May 2014 22:42
Last Modified:23 Sep 2014 19:36

Repository Staff Only: item control page