Structure and Tectonics of Japan Sea and Sikhote Alin and their relation to Japan Arc

1 .在日本盆地的研究在这次合作研究中，POI的R/V gagarinsky教授在俄罗斯专属经济区日本盆地整个区域进行了5英里间隔的海洋调查。地震调查：利用千叶大学海底地震仪和P01单气枪对日本盆地进行地震研究，发现日本盆地中部地壳厚度为8-9km，沉积物厚度为1.5km，并向东增加。地壳的特征与典型的海洋地壳不完全相同。地壳在东部盆地是海洋的一部分,然后中央盆地的一部分,从东部的不同发展模式,即海底扩张development.b.Magnetic调查:一个质子旋进磁力仪POI和STCM (Magnetomete舰载三个组件)的千叶大学被用于磁研究盆地造成的,有明显的磁异常线理在东部盆地的一部分,不是很明显在百磅的部分。这与上面提到的地震调查是一致的。c.重力调查：使用POI的船载重力仪。由重力异常得到的地壳结构由东向西由洋向大陆变化。在锡霍特阿林进行地质调查，利用锡霍特阿林特别是Tercialy时期的地质资料，重建了日本诸岛在日本海打开前的原始位置。结合盆地底地形和日本岛弧的变形等资料，揭示了日本诸岛与西霍特群岛在第三纪的地质延续。

l.Research in the Japan BasinDuring this cooperative research, the marine investigations had been carried out by R/V Prof.Gagarinsky of POI on the tracks of 5 mile interval in the whole area of Japan Basin in the Russian EEZ..a.Seismic investigation : OBSs of Chiba University and the single air-gun of P01 were used for the seismic research in the Japan Basin resulting in that the thickness of crust in the central part of the Japan Basin is 8-9km including 1.5km thick sediments and increasing towards east. The feature of crust is not completely identical with the typical oceanic one.The crust in the eastern part of the Basin is oceanic, then the central part of the Basin has the different developing mode from the east part, namely sea floor spreading development.b.Magnetic investigation : A proton precession magnetometer of POI and a STCM(Shipboard Three Component Magnetomete) of Chiba Univ. were used for the magnetic study of the Basin resulting in that there are clear magnetic anomaly lineations in the eastern part of the Basin and not so clearly in the cental part. This is coincident with the seismic investigation mentioned above.c.Gravity investigation : A shipboard gravimeter of POI was used. The structures of the crust obtained from gravity anomalies change from the oceanic to the continental from east to west.2.Research in the Sikhote Alin (Geological Research)The geological investigation was done to reconstruct the original position of Japanese islands before opening of the Japan Sea using the geological data in the SikhoteAlin especially of Tercialy time. The geological continuation between the Japanese islands and the Sikhote Alin in the Tercially time was revealed taking other data, that are, tobography of the Basin floor and deformation of the Japanese Island Arc into account.