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：日本大学ORI的R/V白丸和R/V Tanseimaru进行了三分量磁测量。1987年6月在东京。三分量异常揭示了地磁异常线形的详细特征。其中一个重要结果是日本海盆海底的磁化强度具有南北偏角，不代表海盆的旋转。(2)大和盆地：1986年夏季通过DELP计划进行了4个层序的磁测。所有4个层序的磁化强度的下降几乎都是正北向南的，表明盆地没有旋转。冲绳海槽地磁三分量异常在冲绳海槽中央的伊赫亚凹陷，地磁异常幅度较大。这些异常可以用正常磁化的海底地貌来解释，表明磁源来自于布伦赫斯期的年轻侵入火山岩。海底磁强计(OBM)测量：在南开海槽北部部署了一台带有新研制的分离装置的海底磁强计，并通过声学分离系统撤离。

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.