Seismic Refraction

Seismic refraction method is also one of the most used methods in engineering applications to obtain the elastic properties of sub-surface. Seismic refraction consists of recording the length of time taken for an artificially provoked surface vibration to propagate through the earth. By processing the data, the seismic velocities and depths of the underlying layers can be determined. These velocities are characteristics of the nature and quality of the bedrock; a fissured, fractured or sheared rock will be characterized by reduced seismic velocities.

This method, even if applicable to offshore surveys, finds its major marine application on surveys along shorelines or over small bodies of water, where it is better-suited than seismic reflection. It provides quantitative information on the quality and depth of sediments and bedrock, on fault zones and on the elastic constants of the rock.

The method is best-suited for sediment thickness analysis, bedrock quality determination, detection of presence of weaknesses in the bedrock, before taking up the erection of any civil engineering structure on the marine bottom.