SCEC Award Number 21110 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title SCEC BBP Enhancement: EAS Scenario and Ridgecrest Sequence Validation
Name Organization
Kim Olsen San Diego State University
Other Participants PhD student, Nan Wang
SCEC Priorities 4a, 4b, 4c SCEC Groups GM, EEII, CS
Report Due Date 03/15/2022 Date Report Submitted 03/16/2022
Project Abstract
The purpose of this project is to validate the SDSU SCEC Broadband Platform (BBP) module using Fourier Amplitude Spectrum (FAS) in addition to the existing Spectral Acceleration metric implemented on the platform, specifically using the smoothed EAS metric (SEAS). We find that the SEAS goodness-of-fit (GOF) reflects that of the pseudo-spectral acceleration (PSA) GOF, with higher sensitivity. A caveat is that the SEAS GOF tends to deteriorate for frequencies higher than about 10-20 Hz, due to the nature of the source time function convolved with the scattering functions used by the SDSU module. Tests with different source time functions and related parameters have not significantly resolved this problem. Based on this result, we have determined that the useful bandwidths from the BBP results obtained by the SDSU module is < 10 Hz for SEAS and < 50 Hz for PSA. We have also validated the July 2019 Ridgecrest sequence (M5.5, M6.4, and M7.1 events), and obtained acceptable results, with additional analysis to be done for the low frequency results of the Ridgecrest B and C events. Finally, we have prepared the SDSU module for the BBP 22.3 release, to occur in March or April of 2022.
Intellectual Merit The introduction of goodness-of-fit (GOF) from the Fourier Amplitude Spectrum (FAS) is an important step forward. FAS includes that linear site response remains linear at all frequencies and does not depend on the spectral content of the input motion, as is the case for response spectra, and calibration of input parameters and methods for finite-fault simulations based on Fourier spectra are more closely related to the physics in the simulations. This work has shown what to expect from GOF results in the FAS domain, and opened avenues for improvement of the BBP modules.
Broader Impacts The new infrastructure on the BBP, as well as the progress from modeling the Ridgecrest sequence, benefit the quality of seismic hazard analysis. As a result, society will be better off in future earthquake hazards. In addition, improvements to the SCEC BBP aids ground motion modelers from around the world, including in the class room.
Exemplary Figure Figure 1. (top) SEAS and (bottom) PSA for 64 realizations of the San Simeon event using the SDSU module. Kim Olsen and Fabio Silva.