Faeroes Large Aperture Research Experiment (FLARE): imaging through basalt

Abstract

The acquisition of high density, large aperture seismic data may allow the deep crustal structure to be studied in areas that have traditionally proven difficult to image using conventional seismic profiling techniques, such as those where high-velocity basalt flows or sills overlie sedimentary sections. This is because the amplitudes of reflections at wide angles are generally much larger than at near normal-incidence, and because large aperture seismic data carries much more velocity information than the limited aperture data recorded along conventional seismic profiles. We discuss the acquisition and processing of synthetic aperture seismic profiles, using two 2D seismic vessels to achieve continuous offsets to more than 38 000 m along profiles near the Faeroe Islands, shot as part of the Faeroes Large Aperture Research Experiment (FLARE). The new technique shows the presence of lava flows extending away from the Faeroe Islands across a thick (up to 4 km), probably Mesozoic and early Tertiary underlying sedimentary section. Seismometers on the Faeroese island of Suduroy show that the sedimentary section pinches out beneath the island, and also provides control on the crustal thinning beneath the region southeast of the Faeroe Islands. Since Tertiary basalt flows and sills are such a pervasive feature of the geology of the highly prospective northwest European continental margins, synthetic aperture profiles are likely to be of considerable importance in the future in imaging sub-basalt structure in these areas.