Ground motion modeling in random geologic media

摘要

Field experiments have shown that scattering by random geologic heterogeneity has a significant influence on explosively induced stress wave propagation. Physical models of stress wave propagation are based on the assumption that the subsurface geologic material can be divided into homogeneous layers. This simplistic approach may be responsible for much of the discrepancy which remains between field experiments and computational results. Stochastic modeling techniques were applied in this study to ground shock propagation through spatially random geologic media. Using these techniques, the spatial variability in the material model is defined by 1) the type of statistical distribution which defines the subsurface heterogeneity; 2) the scale or correlation distance of the variability; and 3) the mean and standard deviation of the material property under consideration. The statistical estimates of the properties are used in the modeling technique. The technique was then incorporated into a finite difference ground shock code to simulate the subsurface inhomogeneities. The stochastic calculational results were compared to homogeneous material model calculations. The comparisons indicate that the introduction of spatial subsurface heterogeneity into ground shock calculations cause changes in ground shock attenuation rates and broadening of peaks relative to the homogeneous calculations.