Simulation of Underground Chemical Explosions in Soft Alluvium, Hard Granite and Brittle Tuff Using Anisotropic Near-Field Hydrodynamic Generated Source Coupled to Far-Field Linear Anisotropic Wave Propagation
Session: Explosion Seismology Applications and Advances II
Type: Oral
Date: 4/19/2021
Presentation Time: 02:45 PM Pacific
Description:
The Source Physics Experiment (SPE) is an ongoing effort to improve explosion monitoring by conducting a controlled series of chemical explosions at the Nevada National Security Site (NNSS) and using the resulting observations to improve and validate physics-based simulations of explosion phenomena. Phase I of SPE was conducted in granite which contains a network of joints. It has been shown through hydrodynamic source modeling that sliding on these pre-existing joints may be the cause of the observed tangential motion. Near-field motions generated with hydrodynamic non-linear source models have been coupled to elastic wave propagation codes to propagate these resulting motions into the far-field domain which is assumed to be elastic. However, one simplification that has been made is that the far-field elastic media is isotropic. This is likely not the case as the network of pre-existing joints also continues outside of the inelastic source region of the SPE and can be shown to result in an anisotropic stiffness for the granite. We use a hybrid modeling approach with one-way hydrodynamic-to-elastic coupling. Near source hydrodynamic motions are computed using GEODYN-L while anisotropic elastic wave propagation is modeled using SW4. The anisotropic material model employed in the SW4 domain is derived from the properties of an observed fracture network with relatively well-constrained joint orientations, spacing, and stiffnesses. We show that consideration of anisotropic material in the elastic regime has an important effect on the propagation of tangential motion. Propagation of motions generated in an anisotropic source region into an isotropic far-field domain will introduce some biases. To illustrate the versatility of the proposed approach, the current GEODYN-L/SW4 coupling has also been applied to model Phase II of SPE, conducted in a dry alluvium geology (DAG) and it is being extended to consolidated pyroclastic or volcaniclastic rocks such as tuffs. Simulation results from anisotropic alluvium, granite and tuff will be presented.
Presenting Author: Souheil M. Ezzedine
Student Presenter: No
Authors
Souheil Ezzedine Presenting Author Corresponding Author ezzedine1@llnl.gov Lawrence Livermore National Laboratory |
Oleg Vorobiev vorobiev1@llnl.gov Lawrence Livermore National Laboratory |
Arben Pitarka pitarka1@llnl.gov Lawrence Livermore National Laboratory |
William Walter walter5@llnl.gov Lawrence Livermore National Laboratory |
Tarabay Antoun antoun1@llnl.gov Lawrence Livermore National Laboratory |
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Simulation of Underground Chemical Explosions in Soft Alluvium, Hard Granite and Brittle Tuff Using Anisotropic Near-Field Hydrodynamic Generated Source Coupled to Far-Field Linear Anisotropic Wave Propagation
Category
Explosion Seismology Applications and Advances