According

to recommendations in Frankowski et al. (2009), the ultimate interpretation of seismo-acoustic data, leading to their conversion into geological cross-sections, should be preceded by drillings and analysis of the drill core samples, as well as verification of the findings of geophysical surveys other selleckchem than acoustic measurements. During the interpretation and processing of the seismo- acoustic data, geological-engineering cross-sections are drawn showing the boundaries between the sediments and the thicknesses of the individual layers. Devices used in seismo-acoustic surveys, known as sub-bottom profiling devices, are constructed in the same way as bathymetric echo-sounders, but they work at lower frequencies, most often not higher than a dozen or so kHz. They also have a higher emitted signal energy in comparison to hydrographic and navigable echo sounders. Geophysical vessels have their seismo-acoustic equipment incorporated permanently in the hull. Smaller craft use towed or side-mounted submerged Raf inhibitor devices. Because these consume a relatively large amount of power, the supply to the sub-bottom

profilers requires 230 V wiring, which is available on bigger vessels only. The StrataBox, produced by SyQwest Inc. (USA), is one of the few devices powered by 10–30 V DC. Having been purchased recently by the Institute of Hydro-Engineering of the Polish Academy of Sciences (IBW PAN), this equipment works with an acoustic frequency of 10 kHz and ensures penetration down to 40 m below the bottom for a sea bed built of cohesive deposits. For sandy sediments, the penetration range is no more than a few metres, but the transducer is light enough for it to be mounted on the side of a small boat. The power supply is 12 V or 24 V (DC). According to the specification sheet, the StrataBox can operate at maximum depth of 150 m; the minimum depth depends on the type of sediment on the sea bed surface. In addition, the user manual recommends find more that the distance between the transducer (its lower submerged surface) and the sea

bottom should not exceed 2.5 m. The surveys described in the present study have proved this minimum distance to be slightly smaller, namely 1.8–2.0 m. Measurements carried out in May 2009 near the IBW PAN Coastal Research Station (CRS) at Lubiatowo focused on surveying the structure of the non-cohesive sea bottom. It was known from analysis of surficial sea bed samples taken previously at Lubiatowo that the sea bottom consists mostly of fine sand with a median grain diameter of d50 = 0.20–0.25 mm; locally it is coarser – d50 ≈ 0.4 mm. The objective of the seismo-acoustic survey using the StrataBox was to determine the thickness and offshore range of the dynamic layer as conventionally defined ( Boldyrev 1991, Subotowicz 1996).