Earth is a blue planet; over 70 percent of its surface is covered by ocean (NOAA, 2014). Life relies on the ocean and its processes, and yet we have only brushed the surface of exploring the realm to its fullest detail. There has been increased focus on better understanding the ocean through ocean exploration and advancements in technology in an effort to map and describe its three regions:  the water column, the seafloor and the sub-bottom floor.

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Studying the sub-bottom seafloor presents its own unique challenges and provides important geological information to a variety of stakeholders; such as, government, industry, universities and research institutions.  Knowledge of the properties, shape and active processes of the seabed is important for a multitude of offshore applications, includng (Fader et al., 2014):

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• Geohazard surveys

• Geological and Geophysical Scientific Research

• Hydrocarbon Exploration

• Extended Continental Shelf Delineation through UNCLOS

• Pipelines and Electrical and Communications Cables Routing

• Seabed Dredging

• Bottom Fishing

• Offshore Wind Farm and Tidal Power Device Siting

• Deep Sea Mining and Sub-bottom Target Identification

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Subsurface seafloor geology is predominantly studied through sampling (i.e. coring, grab samples and dredging), and geophysical methods (i.e. principally acoustic methods).  Sub-bottom profilers (SBP) fall in the category of acoustic remote-sensing techniques, which are non-invasive.  They transmit a low frequency acoustic pulse (lower than conventional echo-sounders) and a portion of this pulse transmits below the seabed and is reflected off layers in the sediments to produce a cross-section of the subsurface (Quinn, 2016). 

 

SBPs are used in geological studies to map the top layers of the seabed and provide quantitative seabed assessment, since properties of the first few meters of the seabed greatly influence the design and planning of offshore oil rigs and other seabed supported structures (Hutchins, McKeown & King, 1976).  High-resolution subsurface seafloor mapping can reveal geological features such as boulders, iceberg furrows, pockmarks, and slumped sediments and can be used to interpret geological hazards, including slumping, shallow gas and faulting, as examples.  Deep ocean mapping is crucial to the hydrocarbon industry, deep sea mining processes along ocean ridges, and is helpful to establish jurisdiction under the Law of the Sea convention. 

 

In choosing a sub-bottom profiler system, there are a number of considerations: vertical resolution, spatial resolution, power, repeatability, and operational logistics.  Often the choice of one parameter is at the expense of others, so the choice is often survey specific.