Sub-Bottom Profiling (High Resolution Seismic Reflection

The seismic reflection method is the most developed geo-physical method due to its widespread use in the oil and gas exploration, the most sought-after natural resource, resulting in a greater share of research and development activity associated with it. For engineering applications, the field procedures and methodology are similar to hydrocarbon exploration but the instrumentation and acquisition parameters have to be designed to obtain the requisite near surface high-resolution data necessary to properly image the structures.

The principle of the method consists of digitally recording the acoustic waves generated at the surface which are reflected back by sub-surface structures or interfaces. A reflection will occur when the density and/or the velocity changes at the boundary between two materials. It is, therefore, possible to detect loose material zones or inhomogeneties of the sub-surface, geological contacts, pipelines, rails etc.

The equipment used requires a very high resolution, and signals of various frequencies can be used. For most of the shallow applications 350 KHz signal is found to be appropriate. The sub-bottom profiler records help in identifying depth and thickness of various sediment layers, presence of pipeline etc., identification of stratigraphy contacts, presence of loose material etc.