On the magnetic anomalies over Toya Lake and its vicinity.
|The aeromagnetic surveys were carried out over and around Toya Lake in July 1964, using a proton magnetometer suspended from the helicopter belonging to the Maritime Safety Agency of Japan. The magnetometer used is of a simple type, with a magnetizing and detecting head coil weighing about 10 kg. It was hung down from the helicopter at a distance of 10 meters. The accuracy of the proton magnetometer is about 士 5 γ for the total intensity of the earth’s magnetic field. The flight path of the helicopter was photographically determined by taking a series of'. terrain pictures with the automatic 35 mm camera. The spacing was about 2 km. The flight was carried out at the heights of 1,100 m and 1,600 m, respectively. From the results obtained, it has been found that there is a remarkable magnetic anomaly of about 400 γ at the central part of Toya Lake in the case of the flight altitude of 1,100 m, and also, there is an anomalous magnetic anomaly of about 1,000 γ over Mt. Usu at the lower altitude. Thus, we have reached the conclusion that the magnetic anomalies can well be revealed by observing the magnetic field characterized by the volcanic rock containing a large amount of magnetite in the region.
|On the magnetic anomalies over Toya Lake and its vicinity.
|Report of Hydrographic and Oceanographic Researches