Site Characterization Based Upon Body-Wave Polarization

Date: 4/26/2019

Time: 02:15 PM

Room: Pine

Body-wave polarization is sensitive to properties immediately beneath a seismic instrument, and has been demonstrated to be effective at estimating the near-surface P- and S-wave speeds (Park & Ishii, 2018). In this presentation, we extend the technique to consider the frequency dependence of body-wave polarization. Since lower frequency waves have longer wavelengths and sample deeper than higher frequency waves, examining the body-wave polarization at various frequencies provides insights into the depth-dependent wave speed beneath a station. Depending on the available frequency range, wave speeds near the surface to the upper crust and beyond can be explored. These results provide invaluable knowledge of the local 1-D structure beyond Vs³⁰, which helps with seismic hazard assessment.

We apply the frequency-dependent analysis to explore near-surface and upper-crustal structure of the continental United States. Our preliminary results show correlation with the geological features and prominent basins, with depth-dependent features that suggest complex subsurface processes at some sites. This versatile technique requires minimal computational resources and can be applied to any single three-component seismograph. It can also provide a means of monitoring changes that occur within the very upper crust caused by volcanic or hydrological processes. It opens a new path to a reliable, non-invasive, and inexpensive way of performing hazard assessment even for locations where drilling or field experiments using vibro-trucks or explosives are not practical options, and reduces uncertainties and ambiguities in resolving near-surface seismic structure.

Presenting Author: Sunyoung Park

Authors