How Much Acoustic Wave Energy Is Converted to Seismic-Wave Energy in Acoustic–Seismic Coupling?

ABSTRACT The interaction between acoustic waves and the ground surface produces surface displacements that are detected by geophones. Seismic waves generated by the coupling of acoustic waves are referred to as acoustic–seismic coupling signals. The conversion of acoustic wave energy into seismic-wave energy during acoustic–seismic coupling has puzzled researchers. In this study, we first defined the potential energy density conversion rate and the energy density conversion rate with reference to the kinetic energy density conversion rate. Then, SPECFEM2D-DG was used to simulate the acoustic–seismic coupling wavefield of the coupling of the atmosphere and various solid media. Our energy density conversion rate better quantifies acoustic–seismic coupling than the kinetic energy density conversion rate. This study aims to determine how much acoustic wave energy is converted into seismic-wave energy during acoustic–seismic coupling. Our numerical results are consistent with the classical concept. The energy conversion from acoustic to seismic waves during acoustic–seismic coupling is less than 1% due to significant differences in physical properties between air and solid media. We also elaborate on why previous research has reported a high kinetic energy density conversion rate of 78% for acoustic–seismic coupling. This discrepancy can be attributed to the coupling mechanism between acoustic waves and the surface, where the normal velocities of acoustic and solid particle motions are continuous. Our results provide a theoretical foundation for deploying observation systems to monitor artificial sources.