In the framework of the 4th International Polar Year Panel “Plate Tectonics and Polar Gateways” the international project “The Dynamic Continental Margin Between the Mid-Atlantic-Ridge System (Mohns Ridge, Knipovich Ridge) and the Bear Island Region” was undertaken in 2007-2008. As a part of this project a new three-component seismic broadband station was installed in September 2007 in the area of the Polish Polar Station Hornsund in Southern Spitsbergen . The new HSPB station has the coordinates: Φ = 77.0019°N, λ = 15.5332°E, H = 11 m a.s.l. During the first years of operation a number of good quality teleseismic events were recorded. This gives the opportunity for a first determination of crustal and mantle structure beneath the station by using receiver function (RF) and SKS splitting techniques. The Moho depth determined using RF is about 32 km beneath HSPB. Significant amplitudes on the transverse components of the RF indicate a shallowly dipping discontinuity (sedimentary-basement) towards the south-west. The fast polarization of SKS phases is near parallel to the border between the continental and the oceanic crust and the Hornsund fault (α = 151.8°). The average time delay dt between “fast” and “slow” directions is 0.68 s, which implies ca. 2% anisotropy in a 100- 200 km thick layer in the mantle.
In marine seismic wide−angle profiling the recorded wave field is dominated by waves propagating in the water. These strong direct and multiple water waves are generally treated as noise, and considerable processing efforts are employed in order minimize their influences. In this paper we demonstrate how the water arrivals can be used to determine the water velocity beneath the seismic wide−angle profile acquired in the Northern Atlantic. The pattern of water multiples generated by air−guns and recorded by Ocean Bottom Seismometers (OBS) changes with ocean depth and allows determination of 2D model of velocity. Along the profile, the water velocity is found to change from about 1450 to approximately 1490 m/s. In the uppermost 400 m the velocities are in the range of 1455–1475 m/s, corresponding to the oceanic thermocline. In the deep ocean there is a velocity decrease with depth, and a minimum velocity of about 1450 m/s is reached at about 1.5 km depth. Be − low that, the velocity increases to about 1495 m/s at approximately 2.5 km depth. Our model compares well with estimates from CTD (Conductivity, Temperature, Depth) data collected nearby, suggesting that the modelling of water multiples from OBS data might be − come an important oceanographic tool.