This marine geophysical survey took place from 03/05/1992 – 10/07/1992 in the Rockall Continental Margin on board the Kommandor Michael. The survey was carried out by the British Geological Survey (BGS). The aim of the survey was to investigate the shallow seismic structure along the eastern margin of the Rockall Bank, Northern Rockall Trough and adjacent banks. Sub bottom seismic profiling data were collected using Airgun, Sparker and Deep Tow Boomer systems. Gravity and Magnetic data were also acquired. These data are archived by BGS. Technical details of the survey are contained in BGS Technical Report WB/92/20C. Brett, CP and Dobinson, A. 1992. Rockall Continental Margin Project. Operations Report. GeoIndex Offshore - https://mapapps2.bgs.ac.uk/geoindex_offshore/home.html?cruise=1992/1_RCK.
Airgun: Source: Cluster array of 4x40 cu in Bolt 600B airguns with wave shape kits, towed at a depth of 2 metres. Number of guns fired selectable but normally all 4 guns used over the majority of the area, reducing to 2 or 1 in the shallow water over the banks. Hydrophone: 24 channel Teledyne T178 with 2 active sections each 75 m in length with a group interval of 6.25m and a 50m stretch section. Channels were summed in groups of 4 to give 6x25m channels. Without active depth controllers the tow depth varied in the range 3.5 to 5m, depending on conditions. Back-up 30m Geomecanique single channel, used on lines 1-3. Sparker: Source: EG&G 9 x multitip array powered by two 232A power supplies and two 231A triggered capacitor banks. Normal operating power was 2000J and firing rate varied from 1 to 3 times during the 10 sec airgun cycle, depending on water depth. Hydrophone: 30m Geomecanique single channel. Deep Tow Boomer: Source: BGS developed deep towed fish based on a Huntec boomer plate. Normal operating power 0.5 kJ to a tow depth of 800m. Hydrophone: short, lm, multi-element array towed behind the fish. Gravity: La Coste and Romberg S75 air-sea gravity meter updated to incorporate a minicomputer for system control and logging of data. Also outputs data to the Qubit Trac IV logging system. Harbour base ties provided using a Worden land meter. Preliminary data reduction was carried out using the BGS PC based processing package to produce crossover errors for data quality control. Magnetics: Barringer M123 marine proton magnetometer with two pen analogue recorder. Data also output digitally to the Qubit Trac IV logging system. Bathymetry: Atlas Deso 20 with narrow beam deep water 33kHz transducer rated to 2200m. Data also output digitally to the Qubit Trac IV logging system. In deep water the first airgun return was digitised to give a depth input to the logging system. Positioning System: VERIPOS differential GPS system hired from Brown and Root Survey. The system was based on a Sercel NR 103 DGPS receiver. This fully integrated unit received both GPS data and differential correction data, carried out the corrections processing and output a differentially corrected positon to the Qubit Trac IV logging system. Correction data was received from shore stations at Wick, Brest (both part of the established VERIPOS network) and Barra. The latter station was set up specifically for this survey but, because of radio licencing difficulties, did not come online until the early part of Leg 2. Two completely independent VERIPOS receivers were operated simultaneously giving 100% back-up. Data Logging System: Qubit Trac IV navigation processor/logger. Using position information input from the VERIPOS system the Qubit systempr oduced navigation information, helmsman display, track plotting and fix outputs to all survey recorders, whilst logging navigation and geophysical survey data at one minute intervals to magtape. Preliminary processing of the logged data was carried out using the BGS PC based processing package for data quality control. For more information see the Cruise Report and associated documentation where available.
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Geophysical Survey 1992/1_RCK: Northern Rockall Trough and surrounding shallow water areas (10/05/1992 to 04/07/1992)
Airgun/Sleeve Gun, Deep Tow Boomer, Echo Sounder, Gravimeter, Magnetometer, Sparker
Available under the Open Government Licence subject to the following acknowledgement accompanying the reproduced British Geological Survey materials "Contains British Geological Survey materials ©UKRI [year]"
CP2 Regional Sea Boundaries: Atlantic North-West Approaches, Rockall Trough and Faeroe/Shetland Channel, Scottish Continental Shelf, Offshore 1:250k: Anton Dohrn, Darwin, Geikie, George Bligh Bank, Harker, Hebrides Terrace, Kennedy, McCallien, Peach, Rockall Island, Rosemary Bank, St Kilda, Offshore 1:500k: Central Hatton, Central Rockall Basin, North Hatton, North Rockall Basin, SeaVoX Sub-Ocean: NORTHEAST ATLANTIC OCEAN (40W)