Study of deep structure of various trench-ridge system, and that of present activity elucidated by micro earthquake observation

本研究“各种沟脊体系的深部结构研究，以及微震观测阐明的现今活动性研究”的目的是研究板块形成部位和板块边界部位的现今活动性和底下结构。为了进行这类研究，必须部署一些地震仪，以便进行自然地震观测和/或进行可控震源地震学研究。从2001年到2004年，我们每年都在各个重要地点成功地进行了敏感的地震研究。许多有趣的地球科学研究地点都在海底之下，因为新的板块只在海底产生，所以灵敏可靠的海底地震仪（OBS）是进行这类研究必不可少的。岛村等人从上世纪60年代末开始成功开发的OBS被广泛应用于本研究。2001年，在土耳其的马尔马拉海和瓜德罗普岛和马提尼克群岛附近的加勒比海进行了两次探险。2002年，科考队在斯瓦尔巴群岛附近的北大西洋-北冰洋地区进行了考察。本研究为控制震源地震学研究，以说明地下深层构造。2003年，探险队在挪威西海岸外的挪威海进行了探险。本研究的目的是阐明大西洋开放的历史，以及大西洋目前的活动和状况。2004年，探险队在阿根廷南部的费戈群岛进行考察，那里是斯科舍板块的板块边界穿过费戈岛的地方。微地震研究说明了现今板块边界的确切位置和板块边界的活动性。

The aim of this research "Study of deep structure of various trench-ridge system, and that of present activity elucidated by micro earthquake observation" was to study present activity and subbottom structure of the sites where plates were made, as well as the sites of plate boundaries.In order to make this kind of studies, it is essential to deploy a number of seismographs in order to make natural earthquake observations and/or to make controlled source seismological studies. Every year from 2001 through 2004 we made successfully sensitive seismographic studies in various important sites.Many interesting sites of geoscience are beneath sea bottom because new plates were only born on the sea bottoms, so that sensitive and reliable OBS (Ocean Bottom Seismographs) are indispensable to make this kind of studies. The OBS, which has been successfully developed by Shimamura and his group since late 1960's, were commonly used in this study.In 2001, two expeditions were made, in the Marmara Sea, Turkey, and in the Carribean Sea near Guadelupe and Martinique Islands. In 2002 the expedition was made in the North Atlantic - Arctic Sea region near Svalbard Islands. This study was for controlled source seismology to illustrate subbottom deep structure. In 2003 the expedition was made in the Norwegian Sea, off the west coast of Norway. The aim of this research was to elucidate the history of the opening of the Atlantic Ocean, and present activity and situation of the Atlantic Ocean. In 2004, the expedition was made in the Southern Argentina, Fiego Islands, where the plate boundary of the Scotia plate crosses the Island. Micro earthquake study has illustrated the exact position of the present plate boundary and the activity of the plate boundary.