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A tomographic image of mantle structure beneath Southern California

Humphreys, Eugene and Clayton, Robert W. and Hager, Bradford H. (1984) A tomographic image of mantle structure beneath Southern California. Geophysical Research Letters, 11 (7). pp. 625-627. ISSN 0094-8276. doi:10.1029/GL011i007p00625.

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We determined the variations in seismic structure beneath southern California by using a tomographic method of inversion on teleseismic P delays recorded with the Southern California Array. The algorithm employed was a modified form of an Algebraic Reconstruction Technique (ART) used in medical X‐ray imaging. Deconvolution with an empirically estimated point spread function was also used to help in focusing the image. The inversion reveals two prominent features beneath the region. The first is a thin, vertical wedge directly beneath the Transverse Ranges that is 2‐3% faster than the surrounding region. This feature deepens to the east, attaining a maximum depth of about 250 km beneath the San Bernardino Mountains. The second feature is a major zone of low velocity material that is 2‐4% slow under the Salton Trough rift valley, extending to a depth of about 125 km. Two possible explanations for the spatial association of the Transverse Ranges with the velocity anomaly below are lithospheric subduction or small‐scale sublithospheric convection in the region of the Big Bend of the San Andreas Fault. The low velocity anomaly beneath the Salton Trough is consistent with convective upwelling there.

Item Type:Article
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Clayton, Robert W.0000-0003-3323-3508
Hager, Bradford H.0000-0002-5643-1374
Additional Information:© 1984 American Geophysical Union. Received January 18, 1984; revised March 15, 1984; accepted March 16, 1984. We thank Sue Raikes for providing most of the teleseismic direct P wave data used in this study, and Marianne Walck for the regional P wave data. Tom Hearn kindly made available his P n time-term results. This work was supported under USGS contract #14-08-0001-21210 and NASA contract NAG-5315. Contribution #4022, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125.
Group:Seismological Laboratory, Division of Geological and Planetary Sciences
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Caltech Division of Geological and Planetary Sciences4022
Issue or Number:7
Record Number:CaltechAUTHORS:20121017-115856637
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Official Citation: Humphreys, E., R. W. Clayton, and B. H. Hager (1984), A tomographic image of mantle structure beneath Southern California, Geophys. Res. Lett., 11(7), 625–627, doi:10.1029/GL011i007p00625.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:34951
Deposited By: Ruth Sustaita
Deposited On:17 Oct 2012 20:35
Last Modified:09 Nov 2021 23:11

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