Refraction and reflection Seismic profilings to investigate Eocene arc

— KY0715 cruise —

Abstract

We carried out a deep wide-angle seismic experiment using a large airgun array and 110 ocean bottom seismographs (OBSs) along the Ogasawara Ridge from 26 November 2007 to December 25 (KY07-15 cruise) using R/V Kaiyo of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). The Ogasawara Ridge is an extinct arc that was produced in Eocene period. In addition, this arc collided with the Ogasawara Plateau and this event is expected to have severely deformed the crust. The objectives of this cruise are to understand the typical characteristics of the Eocene arc and the crustal deformation by collision with the Ogasawara Plateau. An airgun-OBS seismic line with a length of approximately 594 km was set along the Ogasawara Ridge through the gentle southern root near the collision point by the Ogasawara Plateau. We shot a large airgun array with a total volume of 12,000 cu. in. and recorded the seismic signals on OBSs with four components and a 12-channel hydrophone streamer. Moreover, we investigated the northern elongation of the Eocene arc by reflection survey using a G-gun array with a total capacity of 600 cu. in. and a 16-channel hydrophone streamer. In this paper, we summarize the seismic experiments and introduce the OBS data and reflection data.