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Geophysical investigations in the Colorado Delta Region

Kovach, Robert L. and Allen, Clarence R. and Press, Frank (1962) Geophysical investigations in the Colorado Delta Region. Journal of Geophysical Research, 67 (7). pp. 2845-2871. ISSN 0148-0227. doi:10.1029/JZ067i007p02845.

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The combined approach of gravity and seismic refraction techniques was used to determine depths of the Cenozoic section and fault patterns of the Colorado delta region. Bouguer gravity anomalies range from −10 to −88 mgal with respect to the International Ellipsoid, and the trend of isogal contours is northwesterly. In the center of the basin, depths to basement estimated from gravity data are less than known minimum depths determined from seismic refraction profiles. This discrepancy suggests density complexities within the deeper parts of the stratigraphic section, an interpretation that is supported by sparse measurements from well samples; local isostatic compensation may also contribute to the discrepancy but is not thought to be the major cause. Measured seismic velocities ranged from 5650 to 20,000 ft/sec, and several consistent velocity zones were widespread above the pre-Tertiary basement; indicated depths to basement varied from 2200 feet to at least 15,400 feet, the greatest depth being near the international border. Many members of the San Andreas fault system are well delineated by gravity and seismic data, including the Elsinore and San Jacinto faults and a fault beneath the Sand Hills. Of these, the San Jacinto fault appears to be the most continuous through the delta region, but all appear to be en echelon to the trend of the San Andreas fault system as a whole.

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Additional Information:© 1962 by the American Geophysical Union. Manuscript received February 12, 1962; revised May 2, 1962. Standard Oil Company of California released some gravity data for the Imperial Valley and provided a grant-in-aid for the seismic field work. Grateful acknowledgment is made to the Instituto de Geofisica of the Universidad Nacional de México for their collaboration in obtaining gravity measurements in Mexico and to Ing. Julio Monges C., who participated in the field observations. The Texas Company released information on their Grupe-Engebretson well. Special thanks are due Dr. Charles Helsley for his support and advice throughout this investigation. Drs. J. Healy and R. Phinney and Messrs. D. Harkrider and S. Alexander assisted in the field work. Mr. Shawn Biebler provided most of the gravity stations in the Niland-Calipatria area. Additional financial support was provided by the American Petroleum Institute. The final stage of this research was provided for by the National Science Foundation grant G-19778. Drs. Robert P. Meyer and Manik Talwani made valuable criticisms during the preparation of the paper.
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Standard Oil CompanyUNSPECIFIED
American Petroleum InstituteUNSPECIFIED
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Caltech Division of Geological Sciences1069
Issue or Number:7
Record Number:CaltechAUTHORS:20141017-135944181
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Official Citation:Kovach, R. L., C. R. Allen, and F. Press (1962), Geophysical investigations in the Colorado Delta Region, J. Geophys. Res., 67(7), 2845–2871, doi:10.1029/JZ067i007p02845.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50500
Deposited By: Tony Diaz
Deposited On:20 Oct 2014 15:57
Last Modified:10 Nov 2021 18:56

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