3D sub-bottom profiling — High resolution 3D imaging of shallow subsurface structures and buried objects

New developments in sub-bottom profiling brings 3D reflection seismics, routinely used in hydrocarbon exploration, to the shallow survey market by down-scaling the conventional techniques to achieve decimetre resolution imaging of the top tens of metres of the sub-surface in three dimensions. These advances have been made possible by improvement in digital data acquisition and position accuracy. Shallow high resolution sub-bottom profiling currently still relies mainly on single-channel 2D methods. In contrast to the 2D methods that produce individual vertical cross-sections of the sub-surface, the 3D method combines data collected over the survey area into a data volume. The data can then be viewed in any orientation independent of the acquisition direction, delineating structures and objects in three dimensions with enhanced data quality and resolution. The GeoChirp 3D system uses a surface towed structure that comprises source transducers, operating on a bandwidth of 1.5 to 13 kHz, and 60 hydrophone groups mounted on a rigid array. It is positioned using RTK-GPS and a motion reference unit. The integrated deck-end hard and software component combines sonar and navigation data into industry standard SEGY format that are processed and interpreted using readily available software packages. Application examples include small object detection and identification surveys as well as marine archaeology, engineering and geological and geophysical projects.