10. Project NarñIo Iii: Refraction Observation Across a Leading Edge, Malpelo Island to the Colombian Cordillera Occidental

  1. George H. Sutton,
  2. Murli H. Manghnani,
  3. Ralph Moberly and
  4. Ethel U. Mcafee
  1. R. P. Meyer1,
  2. W. D. Mooney1,
  3. A. L. Hales2,
  4. C. E. Helsley2,
  5. G. P. Woollard3,
  6. D. M. Hussong3,
  7. L. W. Kroenke3 and
  8. J. E. Ramirez4

Published Online: 17 MAR 2013

DOI: 10.1029/GM019p0105

The Geophysics of the Pacific Ocean Basin and Its Margin

The Geophysics of the Pacific Ocean Basin and Its Margin

How to Cite

Meyer, R. P., Mooney, W. D., Hales, A. L., Helsley, C. E., Woollard, G. P., Hussong, D. M., Kroenke, L. W. and Ramirez, J. E. (1976) Project NarñIo Iii: Refraction Observation Across a Leading Edge, Malpelo Island to the Colombian Cordillera Occidental, in The Geophysics of the Pacific Ocean Basin and Its Margin (eds G. H. Sutton, M. H. Manghnani, R. Moberly and E. U. Mcafee), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM019p0105

Author Information

  1. 1

    Geophysical And Polar Research Center, University of Wisconsin, Madison, Wisconsin 53706

  2. 2

    Institute For Geosciences, University of Texas At Dallas, Richardson, Texas 75080

  3. 3

    Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii 96822

  4. 4

    Instituto GeofíSico De Los Andes Colombianos, Bogotá, Colombia

Publication History

  1. Published Online: 17 MAR 2013
  2. Published Print: 1 JAN 1976

ISBN Information

Print ISBN: 9780875900193

Online ISBN: 9781118663592

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Keywords:

  • Geophysics—Pacific area—Congresses;
  • Woolard, George Prior, 1908

Summary

Energy critically refracted through the continental crust and mantle as well as the oceanic plate including the zone of subduction has been received by seismographs in the western cordillera of Colombia, South America, from shots fired along a 400-km profile from the Pacific coast to the west. With added control provided by sea gravity data, preliminary results from heat flow, reflection and local refraction measurements at sea, and refraction measurements along the western cordillera, all made during Project Nariño, a model crossing the leading edge of the continent at 4°N has been constructed which satisfies the gravity data both at sea and on land with maximum deviation of 22 mgal. The princinal results from the study are: (1) the verification of structures expected to be associated with subduction by a controlled seismic source technique in an area of active tectonism; (2) a suggestion of a mechanism for localization of sedimentary basins by continental mantle-oceanic plate interaction; (3) a prediction of the extension of the Bolivar Atrato-San Juan basin to the shelf edge; and (4) a beginning explanation of the source of the unusual positive Bouguer anomaly found in association with the high western cordillera of the Andes of Colombia. In the region from the Yaquina graben to the Malpelo rise, uniform delays in the travel times observed as compared to those computed through the model suggest a soft zone in the oceanic upper mantle in accord with a broad zone of higher than normal heat flow which includes the graben. Multiple observations on land of controlled sources fired at sea appear to be a straightforward and effective method of delineating both oceanic and continental structure.