Thunder-induced ground motions: 2. Site characterization

摘要

Thunder-induced ground motion, near-surface refraction, and Rayleigh wavedispersion measurements were used to constrain near-surface velocity structure at anunconsolidated sediment site. We employed near-surface seismic refraction measurementsto first define ranges for site structure parameters. Air-coupled and hammer-generatedRayleigh wave dispersion curves were used to further constrain the site structure by a gridsearch technique. The acoustic-to-seismic coupling is modeled as an incident plane P wavein a fluid half-space impinging into a solid layered half-space. We found that theinfrasound-induced ground motions constrained substrate velocities and the averagethickness and velocities of the near-surface layer. The addition of higher-frequencynear-surface Rayleigh waves produced tighter constraints on the near-surface velocities.This suggests that natural or controlled airborne pressure sources can be used toinvestigate the near-surface site structures for earthquake shaking hazard studies.