Magnetic and Tectonic Trends Over the Hawaiian Ridge

  1. Leon Knopoff,
  2. Charles L. Drake and
  3. Pembroke J. Hart
  1. Alexander Malahoff and
  2. George P. Woollard

Published Online: 18 MAR 2013

DOI: 10.1029/GM012p0241

The Crust and Upper Mantle of the Pacific Area

The Crust and Upper Mantle of the Pacific Area

How to Cite

Malahoff, A. and Woollard, G. P. (2012) Magnetic and Tectonic Trends Over the Hawaiian Ridge, in The Crust and Upper Mantle of the Pacific Area (eds L. Knopoff, C. L. Drake and P. J. Hart), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM012p0241

Author Information

  1. Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 20 APR 2012

Book Series:

  1. Geophysical Monograph Series

Book Series Editors:

  1. Waldo E. Smith

ISBN Information

Print ISBN: 9780875900124

Online ISBN: 9781118663738

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Keywords:

  • Aeromagnetic surveys;
  • Bathymetry;
  • French Frigate Shoals;
  • Hawaiian ridge;
  • Magnetic and tectonic trends;
  • Magnetic anomalies;
  • Magnetic susceptibility employed;
  • Murray and Molokai fracture zones

Summary

In 1965–1966, aeromagnetic surveys were conducted over a strip about 200 miles wide covering the Hawaiian ridge and adjacent areas from the Island of Hawaii to Midway Island. This paper presents analyses of the data collected for that portion of the survey between the Island of Hawaii and French Frigate Shoals. An Apache twin-engined aircraft equipped with a towed Elsec proton magnetometer was used for the survey and was flown at 200 km/hour at an altitude of 3100 meters above sea level. Navigation was controlled with a combined Loran A-Loran C receiver; the magnetic profile crossing errors indicate that the navigational accuracy was of the order of a few kilometers. The magnetometer detector head towed about 25 meters behind and below the aircraft, and the reading frequency was once every 7 seconds. The profiles were spaced 5 to 15 km apart. The results agree very well with those obtained in 1963–1964 for detailed (1-mile) aeromagnetic profiles established over the major islands of the Hawaiian ridge by the authors. Analyses of the earlier measurements showed there is a direct relationship between magnetic anomalies, positive Bouguer gravity anomalies, centers of volcanism, and dike-intruded rift systems where higher than normal seismic velocities are obtained. The new work shows there is a surprising continuity of the magnetic anomalies from east of the Hawaiian ridge across to the area west of the ridge. The strike and location of the magnetic anomaly lineations coincide in general with those of the Murray and Molokai fracture zones. Over the Hawaiian ridge the east-west pattern of anomalies is disturbed by smaller wavelength northwest-southeast striking anomalies and by a complex pattern of anomalies related to local volcanism. In this paper the observed magnetic anomalies are related to bathymetric and structural features and an attempt is made to interpret the magnetic anomalies in terms of geologic structure.