SCEC Award Number 16021 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Inter-Period Correlations of SCEC Broadband Platform Fourier Amplitudes and Response Spectra
Investigator(s)
Name Organization
Jeff Bayless AECOM Andreas Skarlatoudis AECOM Paul Somerville AECOM Fabio Silva University of Southern California
Other Participants
SCEC Priorities 6e SCEC Groups GMP, EEII, GMSV
Report Due Date 03/15/2017 Date Report Submitted 02/14/2017
Project Abstract
 The objective of this project is to continue previous SCEC BBP validation efforts with the implementation of a validation scheme for the inter-period correlation of epsilon for pseudo-spectral acceleration (PSA) and Fourier Amplitude Spectra (FAS) of simulated ground motions. Epsilon is the normalized difference between the observed (or predicted) FAS or PSA and the mean ground motion model predicted natural log FAS or PSA. Ultimately, the intent is for time series from the SCEC BBP to be applied directly in engineering applications, and to do so, the inter-period correlations of epsilon need to be appropriate. The importance of the inter-period correlations of simulated ground motions, and particularly the implications on structural risk, is discussed in Bayless and Abrahamson (2017, in preparation).
In this project, we calculate the correlations of epsilon for both FAS and PSA, for each of the seven western United States Dreger et al. (2013) validation events, plus two additional Japanese events, for the five available simulation methods on the SCEC BBP. The calculated correlations are compared with the observed correlation of FAS from datasets such as NGA-West2 and NGA-East and checked with existing empirical models for PSA. We have provided these results to the SCEC BBP simulation modelers, and have developed plans for collaboration with select modelers to improve the correlations in their models. Our results indicate that there is considerable room for improvement in the simulation methods, particularly at frequencies above 1 Hz.
Intellectual Merit This research is directly related to the Ground-Motion prediction focus group and to refining physics-based simulation methodologies. It contributes to the previous validation efforts of the SCEC BBP by extending them. The validation of response spectra correlations was previously considered by the GMSV TAG, but was too complicated to complete as part of the project led by Nico Luco. The validation of Fourier amplitude spectra has not been previously studied, and should serve as an important link between the simulation modelers (who are generally more familiar with Fourier spectra) and engineering users (who are generally more familiar with response spectra.) With this research, we have equipped both the simulation modelers with the information needed to improve their methods, and the SCEC BBP with the computer codes required to calculate the inter-period correlations for future validations.
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 8. Correlation results for the exsim simulation method, created from a database of 9 validation earthquake simulations.