Design of a 3D Chirp Sub-bottom Imaging System
Rent the article at a discountRent now
* Final gross prices may vary according to local VAT.Get Access
Chirp sub-bottom profilers are marine acoustic devices that use a known and repeatable source signature (1–24 kHz) to produce decimetre vertical resolution cross-sections of the sub-seabed. Here the design and development of the first true 3D Chirp system is described. When developing the design, critical factors that had to be considered included spatial aliasing, and precise positioning of sources and receivers. Full 3D numerical modelling of the combined source and receiver directivity was completed to determine optimal source and receiver geometries. The design incorporates four source transducers (1.5–13 kHz) that can be arranged into different configurations, including Maltese Cross, a square and two separated pairs. The receive array comprises 240 hydrophones in 60 groups whose group-centres are separated by 25 cm in both horizontal directions, with each hydrophone group containing four individual elements and a pre-amplifier.
After careful consideration, it was concluded that the only way to determine with sufficient accuracy the source–receiver geometry, was to fix the sources and receivers within a rigid array. Positional information for the array is given by a Real Time Kinematic GPS and attitude system incorporating four antennas to give position, heading, pitch and roll. It is shown that this system offers vertical positioning accuracy with a root-mean-square (rms) error less than 2.6 cm, while the horizontal positioning rms error was less than 2.0 cm. The system is configured so that the Chirp source signature can be chosen by software aboard the acquisition vessel.
The complete system is described and initial navigational and seismic data results are presented. These data demonstrate that the approach of using fixed source-receiver geometry combined with RTK navigation can provide complete 3D imaging of the sub-surface.
- Design of a 3D Chirp Sub-bottom Imaging System
Marine Geophysical Researches
Volume 26, Issue 2-4 , pp 157-169
- Cover Date
- Print ISSN
- Online ISSN
- Kluwer Academic Publishers
- Additional Links
- 3D Chirp
- 3D seismic
- high-resolution seismics
- seismic sources
- Industry Sectors
- Author Affiliations
- 1. School of Ocean and Earth Sciences, National Oceanography Centre Southampton, European Way, SO14 3ZH, Southampton, UK
- 2. GeoAcoustics Ltd., Shuttleworth Close, Gapton Hall Industrial Estate, NR31 0NQ, Great Yarmouth, Norfolk, UK
- 3. Institute of Sound and Vibration Research, Southampton University, SO17 1BJ, Highfield, Southampton, UK