SCEC Award Number 20133 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title SCEC Simulation Validation for Southern California Basins using Ground Motion Recordings
Investigator(s)
Name Organization
Jonathan Stewart University of California, Los Angeles
Other Participants student TBD
SCEC Priorities 4a, 4c, 4d SCEC Groups EEII, GM
Report Due Date 03/15/2021 Date Report Submitted 03/18/2021
Project Abstract
 We introduce procedures to validate site response in sedimentary basins as predicted using ground motion simulations. These procedures aim to isolate contributions of site response to computed intensity measures from seismic source and path effects. In one of the validation procedures, simulated motions are analyzed in the same manner as earthquake recordings to derive non-ergodic site terms. The validation consists of comparing the scaling with basin depth of simulated vs empirical site terms (the latter having been derived in a separate study). A second validation procedure utilizes two sets of simulations, one that considers 3D basin structure and a second that utilizes a 1D representation of crustal structure. Identical sources are used in both procedures, and after correcting for variable path effects, differences in ground motions are used to estimate site amplification in 3D basins. Such site responses are compared to those derived empirically to validate both the absolute levels and depth scaling of the 3D simulations. We apply the procedure to southern California in a manner that is consistent between the simulated and empirical data (i.e., by using similar event locations and magnitudes). The results show that the 3D simulations over-predict the depth-scaling and absolute levels of site amplification in basins. However, overall patterns of site amplification with depth are similar, suggesting that future calibration may be able to remove observed biases.
Intellectual Merit The project has developed methodologies by which site effects can be inferred from the results of simulations using crustal models that include 3D representations of basins. It has then validated the site response observed from simulations that were run for modest-magnitude events for which ample observations are available.
Broader Impacts The project provided advanced research training to post-doctoral scholar Chukwuebuka C. Nweke, who is from an under-represented ethnic group in earthquake engineering and seismology.
Exemplary Figure Figure 1. Approach 1 site terms for Sa (5.0 sec) as a function of VS30 from 3D simulations using CVM-S4 and CVM-H) for the cases of (a) site response referenced to VS30 = 760 m/s and (b) and site response referenced to an empirical FV model