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Combining Simulated and Empirical Nonergodic Ground Motion Models for Southern California

Description: 

Partially nonergodic ground motion models (N-GMMs) have been developed from simulated data (e.g., Sung and Abrahamson, 2022) and from recorded ground motions (e.g., Parker and Baltay, 2022). Southern California is an example where both N-GMMs can be applied; the Parker and Baltay (2022) model is based on recorded ground motions from the greater Los Angeles region, and Moschetti et al. (2023) is developing similar factors for this region from Cybershake. These approaches have complementary benefits; for example, empirical data is limited at large magnitudes that are well-represented in the simulation data. Conversely, simulated data are limited by the accuracy of the three-dimensional velocity model while empirical data more accurately capture the effects of path and site. We repeat the analyses of Parker and Baltay (2022) using each of the four NGAWest2 ground motion models (ASK14, BSSA14, CB14, and CY14) as a common reference model for the empirical and simulated datasets. We use a maximum likelihood method, as an alternative to the empirical semivariogram approach of Parker and Baltay (2022), to compute the spatial correlation between site response terms as a function of period for each dataset. In addition, we explore using cross-variograms to estimate the spatial cross-correlation between the empirical N-GMM and simulation-based N-GMM as a function of period. Finally, we examine correlations between the simulation factors and surface geology and topography in Southern California. These results combine two sources of constraints on ground motion models and can be used to inform U.S. Geological Survey products such as the National Seismic Hazard Model and ShakeMap.

Session: How Well Can We Predict Broadband Site-Specific Ground Motion and Its Spatial Variability So Far? [Poster Session]

Type: Poster

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: James

Student Presenter: No

Invited Presentation: 

Authors