Overview of the UK ocean-bottom seismology facility: equipment and capabilities, current and future plans
Head, UK Ocean-Bottom Instrument Facility
Department of Earth Sciences, Durham University, DH1 3LE. UK.
In the UK, ocean-bottom seismic data acquisition capability is provided by the Ocean-Bottom Instrumentation Consortium (OBIC) via collaboration between the Universities of Southampton, Durham and Imperial College. OBIC receives partial research council funding to support day-to-day operational activities as part of its national facility status, with remaining funds coming from data acquisition services that it undertakes for academic and commercial applications.
The facility currently operates a fleet of 55 ocean-bottom instrument platforms which can be configured in different ways to suit a wide variety of applications. Fifty of these platforms are configurable as four-component seismographs with geophones and hydrophones or differential pressure gauges as sensors. Nineteen of these platforms are also configurable as EM receivers. In addition, 23 platforms are capable of sampling up to 4 kHz to enable shallow sub-seabed imaging at the high resolutions necessary to investigate the fine-scale detail of the sediment column and the nature of the fluids contained therein.
When used at lower sampling rates, these platforms have a recording duration well in excess of 1 year for passive source acquisition. Consequently, we are currently extending the long-duration recording capability into the broadband domain by inclusion of Trillium Compact three-component seismometers together with hydrodynamic design of their sensor package to minimise coupling to water column currents, whilst maximising coupling to the seabed for both sediment and non-
sediment covered deployment sites. Once we have completed and proven this design, we will engage the user community to seek funding to increase instrument platform numbers further via the establishment of long-term broadband instrument marine networks allied to scientific projects.
Once the broadband development is finished, we will be undertaking a review of our active-source sensor capability and, in particular, running a feasibility study of the use of solid state devices. A further planned development is to build an instrument platform capable of simultaneous and contemporaneous recording of a multitude of geophysical data types using either passive or active controlled-sources (seismic and non-seismic) during the same deployment. Such acquisition ensures all data types are recorded in an identical location and under the same temporal geological conditions, thus optimising their use for the simultaneous and joint inversion schemes which are moving to the forefront of current developments in modelling approaches.