Sea Floor Measurement of Geomagnetic Field Using Newly Developed Ocean Bottom Magnetometers

Abstract

An ocean bottom magnetometer was developed. It is a fluxgate type magnetometer with a triaxial ring-core sensor suspended by a gimbal, and capable of recording the three geomagnetic components in a cassette tape in digital form for more than two months when the sampling interval is 3min. The resolution is 0.8nT in this case. A pop-up system is adopted for recovery, mechanically releasing a weight at a preset time by explosion of gas.
Two sets of magnetometers were used at two sea floor stations on the continental shelf east of the Northeast Honshu in 1981. Of these two sets one is a prototype and the other is an improved version. In the experiment of 1981 the magnetometer of the improved version worked almost perfectly, giving very reliable data of three components of the geomagnetic field. In this paper the details of this successful magnetometer named OBM-C2 as well as the data obtained from the measurements are reported.