Generation of High-Frequency P and S Wave Radiation from Underground Explosions
Final rept. 16 Apr 2008-15 Oct 2011
UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES CENTER FOR EARTH SCIENCES
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The quasistatic damage mechanics formulated by Ashby and Sammis has been made fully dynamic by incorporating the results of recent experimental and theoretical studies of dynamic crack growth. The model has been verified by building it into the ABAQUS dynamic finite element code and using it to simulate high-speed fracture experiments. Simulation of explosions has shown that the spatial extent and pattern of the resultant fracture damage is sensitive to loading rate. High loading rates of short duration produce spherically symmetric compact damage patterns. Slower loading rates of longer duration are more effective in producing long radial fractures. Any asymmetry in the pattern of such radial fractures generates S wave radiation in the far-field, even in the absence of other factors known to generate S waves such as tectonic shear stress or anisotropy in the initial fracture distribution.