Marine seismic surveys
Marine seismic surveying investigates geological structures beneath the seabed by analysing the travel time and reflections of acoustic waves. CERES acquires seismic profiles with equipment selected for the required penetration and resolution.
Principle
An acoustic source emits waves into the seabed. Part of the energy is reflected at interfaces between sediment layers and recorded by receivers. Hydrophones in a seismic streamer measure pressure variations in the water. The resulting profiles help interpret the geometry of subsurface layers.
Equipment
CERES selects the equipment according to the required resolution, penetration depth and site conditions. Available reflection-seismic sources include Innomar sub-bottom profilers, boomers, sparkers and a small-volume air gun.
Seismic refraction equipment can also be deployed from a CERES vessel.
SUB-BOTTOM PROFILER
Sub-bottom profilers image shallow sediment layers at high resolution. Performance depends on the sediment and system configuration.
Frequency: 2–22 kHz
Water-depth range: 1–400 m
Sediment penetration: up to 40 m
Beam angle: 6°
Resolution: approximately 10 cm
SPARKER AND BOOMER
Boomer and sparker systems use acoustic sources suited to greater sediment penetration, with a trade-off between penetration and resolution. Echoes are recorded by a hydrophone streamer. The source and deployment configuration are selected according to the site conditions and survey objectives.
Air Gun
A small-volume air gun provides an acoustic source for deeper investigation. Deployment requires a high-pressure compressor, buffer tanks and a hydrophone streamer. The survey configuration is defined according to the investigation depth and operating conditions.
Processing and Mapping
CERES carries out seismic data acquisition. Except for sub-bottom profiler data, processing and interpretation are performed by a specialist partner.
Deliverables include interpreted horizon maps and raw and processed data in the agreed formats. Available geotechnical data can help correlate the interpreted horizons.
Contact CERES to define a marine ground investigation combining seismic surveys, bathymetry and sampling as appropriate.