The seismic refraction method uses P- and S-wave energy to map vertical and lateral subsurface changes. A hammer blow or explosive charge (the shot) generates a shock wave that travels through the ground which is refracted along material boundaries, and is then received at the surface by sensors (geophones). Refraction interfaces correlate with real world boundaries in the ground, such as soil to bedrock boundaries. Seismic Refraction Tomography is performed on soil and rock sites to generate 2D or 3D compression or shear wave velocity profiles.  These velocity profiles can be used to estimate vertical and lateral variations in soil properties as well as the depth to, shape of and physical properties of bedrock.  Common uses include estimations of depth to and rippability of bedrock, locations of paleochannels, mapping of hypothesized faults, and mapping slide planes of active landslides.  Additionally, P-wave refraction can be combined with Multi-channel Analysis of Surface Waves (MASW) to estimate elastic constants including Poisson’s Ratio and Young’s modulus.  

Applicable on: Soil, rock and paved surfaces.

Test for: Compressional and Shear wave velocity values, soil properties, depth to and shape of bedrock.