Waveform inversion of acoustic waves for explosion yield estimation

Abstract

We present a new waveform inversion technique to estimate the energy of near‐surface explosions using atmospheric acoustic waves. Conventional methods often employ air blast models based on a homogeneous atmosphere, where the acoustic wave propagation effects (e.g., refraction and diffraction) are not taken into account, and therefore, their accuracy decreases with increasing source‐receiver distance. In this study, three‐dimensional acoustic simulations are performed with a finite difference method in realistic atmospheres and topography, and the modeled acoustic Green's functions are incorporated into the waveform inversion for the acoustic source time functions. The strength of the acoustic source is related to explosion yield based on a standard air blast model. The technique was applied to local explosions (<10 km) and provided reasonable yield estimates (<∼30% error) in the presence of realistic topography and atmospheric structure. The presented method can be extended to explosions recorded at far distance provided proper meteorological specifications.

Local Infrasound Variability Related to In Situ Atmospheric Observation

“…The box-and-whisker plot in Figure 4 shows a distribution of SPLs predicted from 20 random realizations of the boundary layer. This distribution can be considered as an empirical probability distribution of sound pressure (Blom et al, 2015;Ostashev & Wilson, 2015) and can be useful to evaluate source inversion uncertainty depending on atmospheric variability (Fee et al, 2017;Kim & Rodgers, 2016;Kim et al, 2015). Although the variance of the prediction uncertainty is related to the characteristic length scale and intensity of the stochastic turbulence, the median predictions are largely impacted by the vertical profile used for atmospheric representation.…”

“…This observation suggests that the SPLs and their large variances were likely caused by the wind variability (Kim & Rodgers, 2017). The sound pressure reduction model is often important to infer source characteristics such as explosion yield (Kim & Rodgers, 2016) and explosive mass flow (Johnson & Miller, 2014;Kim et al, 2015). Without accounting for the atmospheric path propagation effects, the inferred source parameters may suffer from large errors.…”

Seismoacoustic Analysis of Chemical Explosions at the Nevada National Security Site

“…A full waveform inversion technique is employed to estimate explosion yields from acoustic signals. Acoustic signals at local distance, here defined as within 15‐km propagation distance (Kim & Rodgers, ), are inverted for acoustic source time functions which represent expanding volume of air at detonation and can be used as a proxy for explosion energy (Kim & Rodgers, ). Details of the acoustic waveform inversion and associated probability representation were described in Kim et al (), Kim, Rodgers, & Wright, (), and Kim and Rodgers ().…”

“…In this study, we take a time domain approach which provides source time history ( q ( t )) directly without the need of a frequency‐to‐time domain transformation. Kim and Rodgers () showed that the peak mass flow rate corresponds to the reduced acoustic impulse which is a robust source parameter for explosion yield estimation. They related the reduced acoustic impulse I to the yield of explosion based on an air‐blast model: where W is the yield of explosion, I ref is a reference reduced acoustic impulse for 1‐kg TNT explosion, and f t is a scaling parameter.…”

“…A reference acoustic impulse ( I pred ) can be determined from an air‐blast model and the scaling law (Kinney & Graham, ; KG85). Kim and Rodgers () used the KG85 blast model for the reduced acoustic impulse. Blom et al () used a Friedlander waveform to obtain frequency‐dependent acoustic energy.…”