Reconstruction of the Three-Dimensional Acoustic Wavefield Induced by SPE Explosions and Implications for Explosion Yield Estimation

Date: 4/24/2019

Time: 02:15 PM

Room: Cascade I

Underground explosions induce surface ground motions, which can generate acoustic waves in the atmosphere. Since the excitation of epicentral acoustic waves depends on the ground motion, acoustic signals may contain valuable information about explosion source parameters including explosion yield and emplacement (e.g., depth of burial). Previous studies showed that the extent of the epicentral area may not be compact with respect to acoustic wavelengths of interest and the consequent wavefield may not be represented by a simple point source. This finite-size source is expected to excite directional acoustic wavefield whose amplitude strongly depends on azimuth and elevation angle. While the theory predicts complex wavefields, ground-motion induced acoustic wavefield in 3D has not thus far been fully measured nor explored comprehensively. While horizontal variation of the wavefield can be readily recorded by the ground-based acoustic sensor network, vertical variation is very difficult to capture using traditional microphone deployments. This study investigates the three-dimensional properties of the local acoustic wavefield induced by buried explosions during the Source Physics Experiment (SPE) Phase I. As acoustic measurements are limited to the ground for SPE Phase I, we infer the 3-D wavefield by the Rayleigh integral method with epicentral ground motions measured during the experiment. The synthetic wavefield predicted by the ground motion shows remarkably good agreement with the acoustic observations on the ground, which demonstrates that the acoustic wave is a direct response to the epicentral ground motion. We further investigate the directional properties of the induced acoustic waves in the vertical direction and their relationship with the yield and the depth-of-burial of the explosions.

Presenting Author: Keehoon Kim

Authors