LARGE SCALE MODELING OF UNDERGROUND EXPLOSIONS IN FRACTURED GRANITE BASED ON GEOLOGICAL, GEOMECHANICAL AND GEOPHYSICAL CHARACTERIZATION

This work describes a methodology used for large scale modeling of wave propagation from underground explosions conducted at the Nevada Test Site (NTS) in fractured granitic rock mass during Source Physics Experiments campaign. We show that the discrete nature of rock masses is important to understand ground motions induced by underground explosions. In order to build a credible conceptual model of the subsurface we integrated the geological, geomechanical and geophysical characterizations conducted at the NTS. Because detailed site characterization is limited, expensive and, in some instances, impossible we have numerically investigated the effects of the characterization gaps on the overall response of the system. We performed several computational studies to identify the key important geologic features -- joints, faults, saturated versus dry layers, topography etc. -- that affect the most the ground motion in the near-field and in the far-field using stochastic representation of these features based on the field characterizations. Such study would help guiding site characterization efforts to provide the essential data to the modeling community. We validate our computational results by comparing the measured and computed ground motion at various ranges.