Ocean Bottom Seismographs used in a crustal study of an area covered with flood‐basalt off Lofoten, N. Norway

Abstract

ABSTRACTSeismic refraction measurements were made in August 1988 to study the crustal structure off Lofoten, Northern Norway. Twenty‐four 3‐component Ocean Bottom Seismographs (OBS) were used, of which seven were deployed in the area covered by landward‐flowing basalt deposited during the early Eocene break‐up between Norway and Greenland. The main purpose of the OBS survey was to investigate whether this method can be used to map structures below the basalt, which is not easy to penetrate with conventional seismic reflection techniques. The records obtained showed that the OBS data contain considerable information about structures below the flood‐basalt; preopening sediments up to 4.0 km thick is indicated below the 1.0–2.5 km‐thick landward‐flowing basalt. The success of the OBS survey indicates that such measurements can become an important tool in investigations on passive volcanic margins and, potentially, in other areas where highly reflective boundaries make the reflection technique difficult to apply.