SCEC Award Number 21010 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Generation of Broadband Ground Motion from Dynamic Rupture Simulations: A Group Modeling Approach towards better Characterizing Seismic Hazard for Engineering Applications
Name Organization
Kyle Withers United States Geological Survey Shuo Ma San Diego State University Luis Dalguer 3Q-Lab (Switzerland) Yongfei Wang University of Southern California Thomas Ulrich Ludwig Maximilian University of Munich (Germany) Alice-Agnes Gabriel University of California, San Diego Christine Goulet University of Southern California Dunyu Liu University of Texas at Austin Benchun Duan Texas A&M University Jean-Paul Ampuero California Institute of Technology Elif Oral California Institute of Technology Domniki Asimaki California Institute of Technology
Other Participants Yue Du, PhD Student, working with Shuo Ma
SCEC Priorities 4b, 4c, 4a SCEC Groups GM, FARM, CS
Report Due Date 03/15/2022 Date Report Submitted 03/15/2022
Project Abstract
This project works towards improving methods of simulating earthquake ground motions from dynamic rupture simulations for seismic hazard applications via a group modeling effort that incorporates features of the earthquake fault and rupture (through complex fault geometry, stress heterogeneity, etc.) that have been demonstrated from both observations and numerical simulations to affect resulting ground motions. Our investigation analyzes how earthquake rupture characteristics influence ground motion behavior and compares these synthetically generated ground motions with empirical ground motion models (GMMs). The goal of our work is to determine conditions that make broadband synthetic ground motions from dynamic ruptures more reliable in supplementing empirical models with simulation-derived information. We find the aggregated level of ground motion compares well with GMMs in terms of both distance decay and median ground motion at long and intermediate periods (e.g. 0.3-1 s). Some methods have lower than expected amplitudes at shorter periods, a focus of subsequent work. We observe that intra-event variability is highly dependent on hypocenter location, resulting from azimuthal changes in ground motion amplification. In addition to modeling ground motion, we also keep track of fault displacement along the surface trace of the fault, which ensures that we do not create unrealistic source events that may neglect constraints of physical ruptures, We plan to make our database publicly available for use by a variety of end-users and further investigations.
Intellectual Merit This project focuses on generating earthquake sources that produce synthetic ground motion relevant to engineering applications. This group’s goals fall directly in line with the SCEC5 science objectives, as well as the renewed call to ‘develop methodologies to validate ground motions from dynamic rupture simulations for systematic assessment of aleatory variability and epistemic uncertainty in simulated ground motions.’

Our group is a coordinated validation effort to model ground motions from dynamic ruptures. Our research focuses on improving models of earthquake rupture for applications to seismic hazard, utilizing a dynamic rupture approach to validate synthetically generated ground motion, that will both contribute to advancing knowledge in the area of dynamic rupture simulations, as well as understanding how seismic ground motions relate to complex earthquake ruptures.

This work is a continuation of a planned multi-year project. In the future, we envision selecting a few key representative historical earthquakes from the SCEC Broadband Simulation Platform (Goulet et al., 2015) that will be used to further ensure that the ground motion is consistent with that of strong ground motions records. Additionally, validation will be extended to include more complex events, such as both normal and reverse earthquakes, and iteratively expand the range of model parameters, larger domain, higher frequencies, etc... If these initial validation efforts are satisfactory, we plan to begin the process of going beyond the GMPEs, to demonstrate that dynamic rupture simulations have the potential to provide more information to inform seismic hazard for engineering applications.
Broader Impacts This project works towards improving models of earthquake rupture for applications to seismic hazard. This has direct impact to the SCEC research community, especially by potential end users of simulations. The community will benefit from knowing how well the synthetics that result from dynamic rupture simulations compare to observed data or estimates from ground motion prediction equations (GMPEs). The multiple dynamic ruptures approaches used here will ultimately help guide several engineering decisions, such as impacting descriptions of building code and design.

Our group is composed of a broad array of individuals across all stages of career and background, including PhD students and several early-career members, such as postdocs (with representation from several minorities groups as well as international participants).

This project builds a synthetic database of ground motion amplitudes from a diverse range of initial conditions and modeling techniques. Additionally, we also keep track of final fault displacement along the surface trace of the fault. In the future, we intend to make our database publicly available, for use by a variety of other end-users and investigations. For example, it’s likely a few of our simulated events will have similar characteristics to recently recorded events (e.g. the Ridgecrest sequence), that may be used for additional validation and constraint of both surface slip and ground motion amplitudes.
Exemplary Figure Figure 2. (Left) Ground motion trends versus period compared with empirical models for various different initial conditions, including hypocenter location. (Right) Corresponding intra-event standard deviation for a set of rough-fault simulations for Mw ~7, where the hypocenter location are varied. We extract ground motion from 4 leading GMM relations using the values of Z1.0, Z2.5, Vs30, Rjb, etc... used in our simulations. Average trends are plotted in bold, while each individual simulation is plotted as a dashed line.