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Acquisition, processing and analysis of densely sampled P- and S-wave OBS-data on the mid-Norwegian Margin, NE Atlantic


This paper describes the processing and analysis of semi-local OBS-data shot along a 122 km profile in the Vøring Basin, NE Atlantic margin, using both a high-frequency/short shot-spacing and a low-frequency/long shot-spacing air-gun source. Spectral analysis of the data reveals that an important difference between the two sources used, is that the low-frequency source generates significantly more energy around 6 Hz. This higher content of very low frequencies allows detection of arrivals to larger offsets for the low-frequency source. For the nearest offsets (0–20 km) the high-frequency source is able to resolve some more details than the low-frequency source, as far as the shallow to intermediate sedimentary levels are concerned. This is mainly caused by the fact that the high-frequency source has a much sharper primary pulse and reduced bubble pulse compared to the low-frequency source. The data quality can be significantly enhanced by use of band-pass filtering, trace mixing, FK (velocity) filtering, minimum phase predictive deconvolution, as well as Radon filtering. Inspection of particle diagrams documents S-wave splitting, interpreted as microcracks aligned vertically in the sedimentary section by the present day (slightly compressive) stress-field.


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Correspondence to Rolf Mjelde.

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  • Radon
  • Seismic Noise
  • Automatic Gain Control
  • Reduction Velocity
  • Ocean Bottom Seismograph