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

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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.