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Contact: Bob Swift MS F665, LANL, Los Alamos, NM 87545 Voice (505)665-7871 FAX (505)665-3687 bswif@vega.lanl.gov

Geodynamics Studies and Analytical Techniques

Pore Pressure Low-Stress Constitutive Relations: Rocks & Soils Gas Flow and Underground Detonation Calculations Infrasound program & atmospheric propagation Numerical Radiation Hydrodynamics

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Seeking answers to questions about nuclear and conventional weapons effects, detection of clandestine nuclear tests, successful containment of nuclear explosions, and a number of problems in gas and oil extraction requires the ability to model the response of geological materials to large and rapid deformations. The geodynamics section works to develop the computational tools to meet this need and to apply these tools to answering these questions. Our efforts have traditionally been directed towards nuclear test containment problems. Later work has been on a variety of nuclear and conventional weapons effects problems and on problems related to verifying compliance of the former Soviet Union with the Threshold Test Ban Treaty. More recently we have turned our attention to problems in detecting and discriminating clandestine testing by other nations and to problems related to more efficient and economical extraction of natural gas and petroleum. This work has given us strong capabilities in modeling rock and soil behavior under a wide variety of dynamic conditions.

One of the codes we developed to work on these problems is SMC, a finite-difference stress wave code for problems in 1, 2 and 3 dimensions. SMC has an array of highly sophisticated physical models that can simulate dynamics of a nuclear event from the earliest stages of shock coupling in the the rocks, through inelastic stress wave propagation, to the elastic regime hundreds of meters from the detonation. These models also allow simulations of high explosives, fluids and solids subject to impact or a variety of other boundary conditions. SMC provides the important capability of calculating the formation and growth of a nuclear explosion cavity and the final stress state in the rock around the cavity, which is crucial to successful containment of nuclear detonation products. SMC also provides predictions of ground shock characteristics produced by an explosion and can be used to predict source functions for the seismic waves which are generated. These predictions are being used as yield standards for estimating the energy of nuclear explosions, and for studying the effects of near-field rock behavior on the seismic signals that are used to determine if a seismic event is a nuclear or chemical explosion or a natural event.

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