Forward Seismic Modeling: the Key to Understanding Reflection Seismic and Ground Penetrating Radar (gpr) Techniques

Forward modeling of reflection seismic data is a computational process through which a geologic model (units: horizontal distance, vertical depth; layer acoustic impedance) of the subsurface is transformed into a synthetic reflection seismic record (units: horizontal distance, 2-way travel time; reflection amplitude). Synthetic seismic records (synthetics) are often generated both before and after the acquisition of reflection seismic field data. Synthetic seismic records generated before field acquisition are typically used to determine if an intended/expected geologic target will generate an interpretable signature on output processed reflection seismic data. Pre-acquisition synthetic records also aid in selection of appropriate field acquisition parameters. Synthetic records generated after acquisition and processing of seismic field data are used to identify specific reflections (events) observed on field seismic data and to constrain conceptual geologic interpretations. Post-acquisition synthetic seismic records facilitate the interpretation of the processed reflection data, particularly if the corresponding geologic models were generated from “ground-truth” (borehole sonic and density logs). Forward modeling of ground penetrating radar (GPR) data is in many ways analogous to the forward modeling of reflection seismic data. The main practical differences are related to the nature and scale of the geologic (or otherwise) models employed. GPR geologic models depict spatial variations in dielectric constant and conductivity as opposed to acoustic impedance. Units incorporated into GPR geologic models can be as thin as one millimeter (or less), whereas lithologic units incorporated into reflection seismic geologic models seldom have thicknesses of less than one meter.