SCEC Award Number 22056 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Using CyberShake Simulations to Inform Rupture Directivity Modeling
Investigator(s)
Name Organization
Jeff Bayless AECOM Scott Condon AECOM
Other Participants
SCEC Priorities 4a, 4c, 4b SCEC Groups GM, EEII, CXM
Report Due Date 03/15/2023 Date Report Submitted 08/04/2023
Project Abstract
 In this study, a database of near-fault CyberShake simulations, consisting of many earthquake
sources with multiple hypocenters and rupture realizations, is used to evaluate rupture directivity
effects in the simulated ground motions. CyberShake ground motion residuals are calculated from
the Meng et al. (2023; Mea23) ground motion model (GMM) to explicitly quantify the directivity
effects. The overall performance of the Bayless et al. (2020; Bea20) directivity model as compared with the simulation residuals is promising, but wide-ranging. There are many instances of source and hypocenter location with residuals
matching Bea20 quite well, and there are many instances which do not match as well. This is the
same observation Bea20 made with respect to the recorded data used to develop their model.
Peak amplitudes of mean simulation residuals are found to be generally lower than the mean
Bea20 predictions, and the variance of the simulation residuals are found to be generally larger
than Bea20. Nonetheless, modeling improvements gained by incorporating Bea20 are quantified
through residual variance reductions. At T=5 sec, residual variance reductions of between 0.05
and 0.09 are found. This reduction is larger than the empirically derived reduction from Bea20,
which is based on a relatively sparse dataset, and represents about a 12% reduction in one
component of the aleatory variability, which is large enough to be impactful in seismic hazard
applications.
Intellectual Merit This research is directly related to the Ground-Motion prediction focus group and to refining ground motin models. These models have many applications, including their use in physics-based simulations such as SCEC Cybershake and the SCEC Broadband Platform. The results of this research can facilitate future validations of the simulations against recorded ground motions by providing a directivity model.
Broader Impacts This project has supported the already strong collaboration of the group of scientists who work on and for the SCEC broadband platform and CyberShake, by contributing to the research goals and interacting 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 6.
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