Field data often exhibits distortions of primary reflections which are mostly due to near-surface travel-time irregularities. Although such irregularities can be due to subsurface structures, most often they are caused by a shallow, low velocity, unconsolidated weathering layer. Field static corrections are applied to compensate for the effects of variations in elevation, and weathering velocity. The objective is to determine the reflection arrival times which would have been observed if all measurements had been made on a flat plane with no weathering or low-velocity material present. These corrections are based on the refraction first-breaks.by a user-specifiable velocity
Generalized Linear Inversion (GLI)
GLI is a model-based ray-tracing method that assumes the near surface geology is described by layering that exhibits slowly varying thickness, small lateral variations in velocity within a layer and velocity increasing with depth.
TomoPlus offers both conventional and high end near-surface refraction imaging solutions to handle a variety of near-surface problems. In simple situations, conventional approaches are applied to resolve high velocity contrasts and offer high resolution solutions. In complex areas, conventional methods may be applied to derive a good initial velocity model, and then high-end imaging technologies such as traveltime tomography may be further applied to resolve any detail.