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Three-dimensional imaging of steeply dipping structure near the San Andreas fault, Parkfield, California

Louie, John N. and Clayton, Robert W. and LeBras, Ronan J. (1988) Three-dimensional imaging of steeply dipping structure near the San Andreas fault, Parkfield, California. Geophysics, 53 (2). pp. 176-185. ISSN 0016-8033. doi:10.1190/1.1442452.

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Shot gathers from the Parkfield, California, deep crustal seismic reflection line, recorded in 1977 by COCORP, reveal coherent events having horizontal to reverse moveouts. These events were migrated using a multioffset three-dimensional Kirchhoff summation method. This method is a ray-equation back projection inversion of the acoustic wave field, which is valid under the Born, WKBJ, and far-field assumptions. Migration of full-wave acoustic synthetics, having the same limitations in geometric coverage as the COCORP survey, demonstrates the utility of the imaging process. The images obtained from back projection of the survey data suggest that the Gold Hill fault carries ultramafic rocks from the surface to 3 km depth at a dip greater than 45 degrees, where it joins the San Andreas fault, which may cut through more homogeneous materials at shallow depths. To the southwest, a 2 km Tertiary sedimentary section appears to terminate against a near-vertical fault. The zone between this fault and the San Andreas may be floored at 3 km by flat-lying ultramafics. Lateral velocity inhomogeneities are not accounted for in the migration but, in this case, do not seriously hinder the reconstruction of reflectors.

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Clayton, Robert W.0000-0003-3323-3508
Additional Information:© 1988 Society of Exploration Geophysicists. Presented at the 54th Annual International Meeting, Society of Exploration Geophysicists, Atlanta. Manuscript received by the Editor June 2, 1987; revised manuscript received July 27, 1987. Digital data from the COCORP Parkfield survey were kindly provided by S. Kaufman of Cornell University. The work was supported by a generous fellowship from the Amoco Foundation and by grants from Sun Oil Co. and the Keck Foundation. Contribution no. 4475, Division of Geological and Planetary Sciences, California institute of Technology.
Group:Seismological Laboratory
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Amoco FoundationUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
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Caltech Division of Geological and Planetary Sciences4775
Issue or Number:2
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Official Citation:Three-dimensional imaging of steeply dipping structure near the San Andreas fault, Parkfield, California John N. Louie, Robert W. Clayton, and Ronan J. LeBras, Geophysics 53, 176 (1988), DOI:10.1190/1.1442452
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:34886
Deposited By: Tony Diaz
Deposited On:15 Oct 2012 22:43
Last Modified:09 Nov 2021 23:11

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