Design of a 3D Chirp sub-bottom imaging system


Bull, J.M., Gutowski, M., Dix, J.K., Henstock, T.J., Hogarth, P., Leighton, T.G. and White, P.R. (2005) Design of a 3D Chirp sub-bottom imaging system Marine Geophysical Researches, 26, (2-4), pp. 157-169. (doi:10.1007/s11001-005-3715-8).

Download

[img] PDF __userfiles.soton.ac.uk_Users_nl2_mydesktop_Deposits_One off_Bull_et_al_2005_Mar_Geophys_Res_Authorscopy.pdf - Author's Original
Download (1MB)

Description/Abstract

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.

Item Type: Article
Digital Object Identifier (DOI): doi:10.1007/s11001-005-3715-8
ISSNs: 0025-3235 (print)
Keywords: 3D chirp, 3D seismic, chirp, high-resolution seismics, seismic sources
Subjects:

ePrint ID: 24147
Date :
Date Event
June 2005Published
Date Deposited: 23 Mar 2006
Last Modified: 16 Apr 2017 22:41
Further Information:Google Scholar
URI: http://eprints.soton.ac.uk/id/eprint/24147

Actions (login required)

View Item View Item