Seismic Refraction Tomography
It involves an initial velocity model and iteratively traces the rays through the model, comparing the calculated travel time with the measured travel time. This process modifies the original model, repeating until the difference between calculated and measured times is minimized. Ultimately, the goal is to find the minimum travel time between the source and receiver for a source-receiver pair. It is worth noting that building the initial model allows for a subjective and preliminary interpretation based on the professional’s experience and the available information for making this interpretation.

In this way, a realistic subsurface model is constructed, represented by chromatic graphs of the strata, based on compressional wave velocity.

Applications:
-Stratigraphic characterization of the subsurface, determination of the depth of the bedrock substrate and its morphology.
-Definition of the thickness of an altered rock layer.
-Definition of Vs and Vp for the determination of mechanical parameters (Poisson's coefficient and Elasticity-Deformation Moduli, Dynamic Elasticity, Shear-Young Gdin, Volumetric Compressibility, and Dynamic Endometric).
-Geomechanical classification of rock. Definition of the Q index and Emass (Static Deformation Modulus) of Barton.
-Definition of other geotechnical parameters such as the fracturing index (RQD), density (sedimentary rocks), and porosity (sandstones).
-Site characterization for seismic risk assessment (combination with shear wave analysis and the Nakamura method).
-Characterization of tunnel entrances.
-Determination of rippability, the ability of a rock to be fractured or moved by heavy machinery.
-Assessment of deposits of gravel, sand, clay, and construction materials.