In order to compare the results obtained with our system with other techniques, we organized a survey in the Bay of Brest, where seismic data had been recorded a few years earlier, with a sparker system. The difficulty here was to be able to perform the survey as close as possible to the seismic lines. This area is covered with sediments with rocky layers underneath, more or less altered.
Water depth was 15-20m. Seismic data are rapidely limited with the multiples, and by the reflexions on the hardest layers. Penetration in the harder layers is basically zero.
On the resistivity image, the white line is the seafloor. The resistivities goes from blue (low resistivities), basically the sediments more or less compact and soaked with seawater, to red for the highest resistivities, interpreted as the rocky substratum. Rocks can be altered and therefore can show lower resistivities (in yellow or orange). The black line represents the transition between the 2 materials, corresponding to a rapid transition of the resistivity values.
The numbers from 1 to 6 show different features one can find in both models to compare how these structures are described with the 2 techniques.
The MAPPEM system provides much deeper penetration, and is not being limited by transition between the layers. Therefore the MAPPEM system can provide more detailed information of the substratum.Results:
The MAPPEM system can provide other information than seismics, and does not have the limitations of seismics.Added value:
The MAPPEM system penetration is not limited by water depth. Penetration is higher.
Resistivity can provide information in hard rocks.