Preliminary Results on Fully Nonergodic Ground Motion Models in Central California Using NGA-West2 and SCEC CyberShake Datasets

Xiaofeng Meng, Christine A. Goulet, Kevin R. Milner, & Scott Callaghan

Published August 15, 2018, SCEC Contribution #8612, 2018 SCEC Annual Meeting Poster #024

A key input to probabilistic seismic hazard analyses (PSHA) is the total standard deviation of the misfits between ground motion observations and the median ground motion models (GMMs, a.k.a GMPEs), commonly known as σtot. The most promising way to reduce hazard is to reduce σtot through the removal of the ergodic assumption. Although the strong motion networks has been rapidly growing in recent decades, in most cases the empirical data are still too sparse to establish a fully nonergodic model. In comparison, numerical simulations can generate large ground motion datasets at any desired site, which are optimal to reduce σtot by identifying and removing repeatable effects in a fully nonergodic model. However, before the simulation-based σtot can be adopted by engineers in PSHA applications, it is crucial to validate the simulated ground motions against empirical data and models.

In this study, we evaluate the ability of the Southern California Earthquake Center (SCEC) physics-based CyberShake platform to capture the repeatable source, site and path effects from the empirical data. CyberShake Study 17.3 was computed for central California and generated over 285 million ground motion seismograms at 334 sites. We estimate the source, site and path effects by applying the mixed effects regression model to the CyberShake dataset at 3s period and compare them with results from a subset of NGA-West2 dataset in the same area. Preliminary results suggest that the correlation of site effects between CyberShake and NGA-West2 is relatively stable, while the path effects show a wide range of correlation coefficients, indicating a potential mismatch between the simulations and the recorded. We also found good agreement between the source effects obtained from the CyberShake model and stress drop maps for California. This presentation will summarize these results from our analyses.

Meng, X., Goulet, C. A., Milner, K. R., & Callaghan, S. (2018, 08). Preliminary Results on Fully Nonergodic Ground Motion Models in Central California Using NGA-West2 and SCEC CyberShake Datasets. Poster Presentation at 2018 SCEC Annual Meeting.

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