SCEC Award Number 17061 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Improving Site Response Characterization from Surface Waves
Investigator(s)
Name Organization
Victor Tsai California Institute of Technology
Other Participants Daniel Bowden
SCEC Priorities 4a, 4d, 4b SCEC Groups CS, GM, Seismology
Report Due Date 06/15/2018 Date Report Submitted 06/14/2018
Project Abstract
 The standard definition of site amplification characterizes the effects and resonances of vertically-incident body waves, but is inadequate to also describe surface waves. This difference in response to a geologic structure or profile can be shown through preliminary analytic and numerical simulations, indicating a different amount of amplification and a different frequency of peak amplification for surface waves. We propose a more thorough study to understand the extent to which this difference affects seismic hazard estimates for southern California. Tests of the analytic theory are done using data from northeast China. The results are favorable, suggesting the one-dimensional theory adequately explains the majority of observed amplification in the 2-10 second period band.
Intellectual Merit The project has tested the ability of one-dimensional models to accurately predict amplification of various wave types. The success demonstrates that a majority of amplification by structure at a range of frequencies can be understood with simple 1D calculations rather than needing computationally intensive 3D numerical simulations.
Broader Impacts One graduate student has been educated. The project eventually may help improve ground motion prediction equations (GMPEs) that are used for earthquake building codes.
Exemplary Figure Fig. 2: (a) Schematic of the 2 cases examined. (b) Observed vertically incident SH waves at a basin site (NE8H) and reference site (MDJ). (c) Observed Love waves at a basin site (NE8H) and reference site (MDJ). (d) Observed and modeled vertically-incident SH amplification. (e) Observed and modeled Love-wave amplification, averaged over all near-surface earthquakes.