SUB-BOTTOM PROFILING

Sub-bottom profiling (SBP), in this case, refers to the high-resolution characterization of sediments and rock under bodies of water using tow-able chirp/ping system.

Marine geological profiling allows us to detect and to map interfaces between the various sedimentary layers or the overburden / bedrock interface beneath a body of water. The technique is based on the principles of seismic reflection, i.e. the emission of a seismic wave into the subsurface, and the reception of the energy reflected by the various interfaces.

With SBP systems, there is a trade-off between resolution and signal penetration. Geophysics GPR has a range of frequencies available to meet your requirements.

Sub-bottom profiling systems identify and measure various marine sediment layers that exist below the sediment/water interface. These acoustic systems use a technique that is similar to single beam echo sounders. A sound source emits an acoustic signal vertically downwards into the water and a receiver monitors the return signal that has been reflected off the sea floor. Some of the acoustic signal will penetrate the seabed and be reflected when it encounters a boundary between two layers that have different acoustic impedance. The system uses this reflected energy to provide information on sediment layers beneath the sediment-water interface.

Acoustic impedance is related to the density of the material and the rate at which sound travels through the material. When there is a change in acoustic impedance, such as the water-sediment interface, part of the transmitted sound is reflected. However, some of the sound energy penetrates through the boundary and into the sediments. This energy is reflected when it encounters boundaries between deeper sediment layers having different acoustic impedance. The system uses the energy reflected by these layers to create a profile of the marine sediments. Several sonar parameters (output power, signal frequency, pulse length and processing techniques) affect the instrument performance.