Publication Date:
2012-04-15
Description:
ABSTRACT Wide-angle seismic data acquired by use of air-guns and ocean bottom seismometers (OBS) contain strong direct water arrivals and multiples, generally considered as noise and thus not included in the modelling. However, a recent study showed that standard ray-tracing modelling of the water multiples recorded off the Bear Island, North Atlantic, provided a reliable estimate of the velocity distribution in the water layer. Here, we demonstrate that including the amplitudes in the modelling provide valuable information about the V P contrast at the seafloor, as well as the V P /V S ratio and attenuation ( Q P ) of the uppermost sediments. The V P contrast at the seafloor is estimated at about 250 m/s, within a precision of approximately ±30 m/s. The V P /V S ratio in the uppermost sedimentary layer is modelled in the range 2.25–2.50 and the Q P factor is estimated at 1000 for the water, 30–50 for the uppermost layer and 40–50 for the second sedimentary layer. The values obtained for the sediments suggest a lithology dominated by silty clays, with porosity below average.
Print ISSN:
0016-8025
Electronic ISSN:
1365-2478
Topics:
Geosciences
,
Physics
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