Airborne and Shipboard Magnetic Surveys in the Western Pacific Ocean and Sea of Japan

  1. Leon Knopoff,
  2. Charles L. Drake and
  3. Pembroke J. Hart
  1. Takuichi Matsuzaki and
  2. Shinkichi Utashiro

Published Online: 18 MAR 2013

DOI: 10.1029/GM012p0198

The Crust and Upper Mantle of the Pacific Area

The Crust and Upper Mantle of the Pacific Area

How to Cite

Matsuzaki, T. and Utashiro, S. (2012) Airborne and Shipboard Magnetic Surveys in the Western Pacific Ocean and Sea of Japan, 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/GM012p0198

Author Information

  1. Hydrographic Ofice, Maritime Safety Agency, Tokyo, Japan

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;
  • Airborne magnetic surveys;
  • Hydrographic Office;
  • Japan trench;
  • Marine magnetic surveys;
  • Northeastern Honshu;
  • Volcanoes;
  • Yamato bank

Summary

The Hydrographic Office, Maritime Safety Agency of Japan, has performed airborne and shipboard magnetic surveys in the western Pacific Ocean and Sea of Japan. A proton magnetometer towed behind a ship was used for the marine magnetic surveys around the Japan trench off the coast of northeastern Honshu and the Yamato bank in the Sea of Japan. The spacing was about 5 miles. From the results of these detailed magnetic surveys, it was found that there were magnetic anomalies over and around the Yamato bank and Japan trench. Detailed aeromagnetic surveys have been carried out over the land area including volcanoes in Hokkaido and Kyushu, Japan. Geomagnetic total force was measured with a proton magnetometer suspended from a helicopter. The spacing between the track lines was about 2 km. The results of these surveys revealed that there is a remarkable magnetic anomaly, having both positive and negative sign, accompanying a volcano. It is assumed that the anomalies are caused by a magnetic dipole magnetized uniformly in the present earth's magnetic field. According to the Japanese Program of World Magnetic Survey, aeromagnetic surveys in the seas adjacent to Japan have been carried out with an airborne magnetometer installed in the aircraft. The airborne magnetometer consists of a three-component saturable core, gimbals, servo driving system to keep the detector system vertical, fish-eye camera to determine true north, and two kinds of recorders. From the observed data, magnetic charts of the seas adjacent to Japan were compiled on a scale of 1:2,500,000, using polynomials and least squares, for seven components of the earth's magnetic field: D, H, I, F, X, Y, and Z, 1965.0.