Seismic Survey
Seismic prospecting involves measuring the propagation time of a sound wave in the sediment layers of the seabed.
This measurement allows us to visualize deep geological structures through the analysis of seismic wave echoes.
Principle
An acoustic wave (NB) is transmitted into the subsurface, where it reflects from the different interfaces (R1 and R2) and is recorded on return by receivers (NN). Hydrophones installed in the seismic streamer measure variations in water pressure relative to hydrostatic pressure.
Equipment
The CERES team uses equipment adapted to each type of mission, depending on the resolution and depth of penetration required.
For seismic reflection, in order of penetration, CERES uses Innomar type sediment sounders, Boomer or sparker, a small volume air gun.
It is also possible to connect seismic refraction equipment from the CERES vessel.
SUB-BOTTOM PROFILER
A sediment profiler allows measurement of the first few meters of the seabed. Penetration is limited, but resolution is optimal. This equipment is very easy to deploy.
Frequency: 2 to 22 kHz
Range: 1 to 400m
Penetration: max 40m
Opening of the Cone: 6°
Resolution: 10 cm
SPARKER AND BOOMER
These systems transmit a higher-energy acoustic pulse, increasing penetration into the sediments at the expense of resolution. A hydrophone streamer is often required, which makes deployment more complex but significantly improves data quality and processing. A sparker cannot be used in fresh water.
Air Gun
An air gun provides the greatest penetration, but deployment is complex and requires a high-pressure compressor and buffer tanks. An offset hydrophone streamer is also mandatory.
Processing and Mapping
With the exception of the sediment sounder, only the acquisition is carried out by CERES; the processing and interpretation of the data are carried out by another company.
At the end of the work, it is provided with the mapping of the different horizons as well as all the raw and processed data in the requested format.
A preliminary study can also be carried out in addition to geotechnical data in order to identify the Horizons.