SCEC Award Number 17149 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Fourier-spectra based empirical site amplification modeling
Name Organization
Jeff Bayless AECOM Paul Somerville AECOM Andreas Skarlatoudis AECOM
Other Participants
SCEC Priorities 4b, 4c, 4a SCEC Groups GM, EEII
Report Due Date 06/15/2018 Date Report Submitted 11/21/2018
Project Abstract
Currently, there are relatively few options on the BBP for site amplification. The most commonly used model adjusts the Fourier amplitudes of the time series simulated for rock conditions using either the Campbell and Bozorgnia (2013) or Boore et al. (2013) models. Both of these models were created for response spectra even though they are being applied to Fourier amplitudes. The Shi and Asimaki (2017) model is ready to be implemented; this model combines a Vs profile generator with an analytic nonlinear site response. A model by Hashash et al. (2018) is also under development; this uses the Shi and Asimaki (2017) approach with many randomized profiles to develop average amplitude and phase factors. This approach requires validation, as encountered through similar work in the central and eastern U.S., where bias in the simulations results was encountered for some conditions (Stewart et al. 2017a).

The objective of this project was to develop a Fourier-based empirical site amplification model for use on the SCEC BBP to supplement the above methods. We used data recorded in California and Nevada, but the model was not finalized because the observed nonlinearity was not statistically significant for critical Vs30 bins. We expect this will be resolved in the proposed continuation project (2019 proposal submitted to SCEC) by refining the analysis region, expanding the database of recorded ground motions, and supplementing the analysis with simulations.
Intellectual Merit will update upon submission of the final project report
Broader Impacts This project has supported the already strong collaboration of the group of scientists who work on and for the SCEC broadband platform, by contributing to the research goals and interacting on a regular basis with scientists (and engineers.) Possible benefits of the activity to society involve the improvement of earthquake simulations, which will eventually be used in seismic design, particularly for near fault ground motions.
Exemplary Figure Figure 1. Variation of site amplification factors (residuals from the rock condition FAS GMPE) versus peak ground acceleration (rock conditions) binned by Vs30. The red line is the nonlinear fit (see Equation 2) and the magenta and blue lines are the nonlinear models by Hashash et al., (2018) and Seyhan and Stewart (2014).