Integrated geophysics for mapping of soil depth and rock properties in water passages

Important results from the project

This is a feasibility study of how fiber optic cable as an acoustic sensor can be applied in engineering geological seismic surveys. The project has compared a fiber optic seismic system from Silixa, Carina, with hydrophones. In addition, geoelectric measurements was performed to create a complete geophysical dataset for further analysis and to obtain reference data to verify seismic results. We conclude that fiber optic cable placed on the seabed without further coupling than its own weight can be a very good sensor for measuring refraction waves.

Expected long term effects

Fiber optic cable placed on the seabed without additional coupling than its own weight seems to be a very good sensor for measuring refraction waves. Due to the type of fiber cable used in this study, velocity below 3000 m/s have not been possible to study, therefore it cannot be concluded that it can also measure direct waves in water or soil. Based on the results, it looks like optical fiber may in the future be a powerful tool for seismic measurements for integrated geophysical surveys in infrastructure projects.

Approach and implementation

The project was carried out as a practical field study where fiber optic cable was tested together with conventional equipment under the same conditions that prevail in real life investigations for infrastructure projects. As optical fiber systems are new technology under constant development, they are linked to high costs, and because of this it was only possible to carry out a full-scale field trial. Parts of the results are very promising, but further attempts would be needed to verify all the set goals.