Modelling infrasound signal generation from two underground explosions at the Source Physics Experiment using the Rayleigh integral

Abstract

We use the Rayleigh integral (RI) as an approximation to the Helmholtz-Kirchoff integral to model infrasound generation and propagation from underground chemical explosions at distances of 250 m out to 5 km as part of the Source Physics Experiment (SPE). Using a sparse network of surface accelerometers installed above ground zero, we are able to accurately create synthetic acoustic waveforms and compare them to the observed data. Although the underground explosive sources were designed to be symmetric, the resulting seismic wave at the surface shows an asymmetric propagation pattern that is stronger to the northeast of the borehole. This asymmetric bias may be attributed to the subsurface geology and faulting of the area and is observed in the acoustic waveforms. We compare observed and modelled results from two of the underground SPE tests with a sensitivity study to evaluate the asymmetry observed in the data. This work shows that it is possible to model infrasound signals from underground explosive sources using the RI and that asymmetries observed in the data can be modelled with this technique. & copy; 2014 Published by Oxford University Press on behalf of The Royal Astronomical Society 2014. This work is written by (a) US Government employees and is in the public domain in the US.