What can we get out of acoustic coda from explosions?

Thursday, 18 December 2014: 2:55 PM
Omar E Marcillo1, Stephen Arrowsmith1 and Rodney W Whitaker2, (1)Los Alamos National Laboratory, Los Alamos, NM, United States, (2)Los Alamos Natl Lab, Los Alamos, NM, United States
By analyzing blast waves from chemical explosions, detonated at the same location and recorded at short distances, we found features that repeat in amplitude and phase consistently between explosions and can last several seconds. We call this part of the waveform signal the acoustic coda. We modeled these features as reflected and/or scattered waves by acoustic reflectors/scatters surrounding the explosions. The acoustic coda is sensitive to changes in the atmospheric conditions and location of background scatters, and can be used to extract information of such changes. For example, we have demonstrated a technique to recover differential air temperatures around explosions using small changes in the phase of the acoustic coda. This technique provides an estimate of changes in bulk air temperature that are averaged over the path. Also, as the coda is very sensitive to changes in the location of background scatters, we are exploring the use of relative phase delays and amplitude changes within the coda to study changes in the location and the characteristics of the surroundings of the source.