On the aeromagnetic surveys in the Kagoshima Bay and its vicinity.

Abstract

The aeromagnetic surveys were carried out in the Kagoshima Bay and its vicinity in November 1964. The total coverage of the surveys was 60 km×70 km including Sakurajima, an active volcano, and the Kagoshima Bay. The average spacing between the track lines was about 2 km. The flight altitude was about 2,000 m. Geomagnetic total force was measured with a proton magnetometer suspended from the helicopter in the same way as in the aeromagnetic surveys over and around Toya Lake. The results of the surveys are summarized as follows : (1) Mt. Sakurajima has a remarkable magnetic anomaly of about 400 γ. It is assumed that this anomaly is caused by a magnetic dipole magnetized in the present earth’s magnetic field. (2) There is a remarkable magnetic anomaly of about 150 r around the mouth of the River Beppu. ( 3) There is an anomalous magnetic anomaly of 170 r over the area about 15km east of Kushikino. (4) There is a big magnetic anomaly of about 400 γ accompanying Mt. Kaimondake. Studying the correlation between these magnetic anomalies and the geological structure in the Kagoshima Bay and its vicinity, it has been found that there is no magnetic anomaly around the area extending from Kagoshima City to Ikeda Lake and there is no magnetic rock containing any amount of magnetite in this area.