Three component geomagnetic anomalies in backarc basins (e.g. Japan Seq and Okinawa Trough)

1. 日本海地磁三分量异常(1)日本盆地：1987年6月，东京大学ORI的R/V Hakuhomaru和R/V Tanseimaru进行了三分量磁测量。三分量异常揭示了地磁异常线的详细特征。其中一个重要的结果是，日本盆地海底磁化具有南北赤纬，这并不意味着盆地的旋转。(2)大和盆地：1986年夏季通过DELP程序进行了4个层位的磁测量。所有4个序列的磁化磁偏角几乎都是南北方向的，这表明盆地没有旋转。冲绳海槽的地磁三分量异常在冲绳海槽中部的Iheya凹陷存在较大幅度的地磁异常。这些异常与正常磁化的海底地形有关，表明磁源为布吕士期年轻的侵入火山岩。海底磁强计（OBM）测量：在南开海槽北部部署了一台海底磁强计，并配备了新研制的分离装置，通过声波分离系统进行了回收。

1. Geomagnetic three component anomalies in the Japan Sea(1) Japan Basin: Three component magnetic survey was conducted by R/V Hakuhomaru and R/V Tanseimaru of ORI of Univ. of Tokyo in June 1987. The detailed feature of geomagnetic anomaly lineations was revealed by the three component anomalies. One of the important results is that magnetization of the Japan Basin seafloor has the north-south declination which does not suggest rotation of the basin.(2) Yamato Basin: The magnetic survey over 4 seqmounts was conducted through the DELP program in summer 1986. The declinations of magnetization of all 4 seqmounts direct almost due north-south, which suggest no rotation of the basin.2. Geomagnetic three component anomalies in the Okinawa TroughIn the Iheya depressionm the central part of the Okinawa Trough there are large amplitude geomagnetic anomalies. These anomalies are explained by the seafloor topography with normal magnetization, which suggests that the magnetic source is the young intrusive volcanic rocks in the Brunhes epoch.3. OBM(Ocean Bottom Magnetometer) survey: An OBM with newly developed detach device was deployed in the north of Nankai Trough and withdrew by an acoustic detach system.