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Infrasound propagation with realistic terrain and atmospheres using a finite-difference time-domain method

Numerous infrasound observations and complementary numerical simulations have shown that infrasound propagation is strongly influenced by terrain within approximately 10 km from the source. Recent computational efforts using ray theory have shown that terrain influence extends over hundreds of km and is especially strong for waves ducted in the troposphere. Wind and temperature gradients also have a strong influence on propagation at these distances, which suggests that both terrain and atmospheric structure need to be accounted for in waveform modeling at a wide range of distances. Here we show preliminary results from numerical simulations of linear acoustic propagationthrough a moving, inhomogeneous atmosphere using a finite-difference time domain propagation code. We compare our synthetic waveforms in two and three dimensions with existing community infrasound propagation codes and discuss future developments, including open source licensing. Finally, we present preliminary comparisons between modeling and observations from a large-scale explosion at the Utah Testing and Training Range. This scenario highlights the importance of using full-wave modeling compared to ray methods to explain the observed waveforms. [Work funded by the Defense Threat Reduction Agency. Cleared for release.]