As refraction tomography increases the ability to meet project objectives and present 2D color images more representative of the subsurface, we begin to approach the end users needs. That is, the end product from a refraction survey can be either a 2D image or a full 3D model. Full 3D earth models can be used for many purposes after the geophysical survey is complete. Subsurface physical property data (i.e., velocity, density, etc.) in 3D model space permits assessment of a site from a whole new perspective. For example: structural loading, seismic loading, or construction excavation requirements can all be uniquely handled with a 3D model.
This paper presents an advanced approach to refraction data processing presentation, and visualization. This new approach is called the Geostructural Analysis Package (GAP). GAP incorporates several numerical modeling processes: discrete element method, particle flow code, finite differencing, and the material point method. These four numerical modeling methods have been combined and optimized for seismic applications. GAP represents an innovative approach to allow better data analysis and presentation. Geophysical data are processed to produce 3D volumetric models for further analysis by an end user. For example, mapping top-of-rock may be the objective of a particular geophysical investigation, but it is not the engineering purpose of the survey (e.g., construction of critical structures – a dam or a bridge foundation). With better 3D earth models, rather than 2D images, engineers are more likely to use geophysical results by incorporating them directly into engineering design and analyses.
Full 3D model results from case histories will be presented to show the benefit of processing and presenting seismic refraction data using a new perspective – 3D GAP modeling. GAP represents the newest advancement in subsurface modeling using refraction data.