SCEC Award Number 22043 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
Investigator(s)
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 Alice-Agnes Gabriel University of California, San Diego Christine Goulet University of Southern California Benchun Duan Texas A&M University Dunyu Liu University of Texas at Austin Jean-Paul Ampuero California Institute of Technology Elif Oral California Institute of Technology Thomas Ulrich Ludwig Maximilian University of Munich (Germany) Domniki Asimaki California Institute of Technology
Other Participants Yue Du, PhD Student, working with Shuo Ma
SCEC Priorities 4a, 1d, 4e SCEC Groups GM, FARM, CS
Report Due Date 03/15/2023 Date Report Submitted 03/15/2023
Project Abstract
 This work uses a group modeling approach to simulate ground motions from physics-based dynamic earthquake rupture simulations. Our purpose is to supplement sparse empirical ground motion data, to ultimately help inform seismic hazard assessment. Using a collaborative approach composed of six modeling groups, we focus our efforts at near-source distances, comparing simulated metrics with empirical predictions at frequencies up to ~3 Hz. We begin with an analysis of our synthetic results compared with ground motion models (GMMs) and are compiling a database of source ruptures and corresponding synthetic ground motion information for use in engineering efforts and other research studies.

We first focus on strike-slip earthquakes, across a magnitude range where the ruptures are spontaneously nucleated, allowing ruptures to die-out naturally. Each modeling group uses their preferred method of initial friction, fault geometry, and stress conditions to simulate ruptures, but we impose common constraints of some predictor variables (such as site conditions), to enable uniform comparison with empirical models. This method allows a diverse set of ruptures and ground motions and highlights the impact of various choices of parameter combinations on ground motion trends. We are finding that the averaged ground motion results have similar characteristics with that of predicted GMMs, including distance trends at both long and short distances from the simulated earthquakes. The median and within-event variability of the data are analyzed, with variations correlated with choice of individual modelers’ initial conditions. This finding illuminates the importance of considering multiple source characteristics in the earthquake source generation.
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.
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 3. Bias plot showing the difference between empirical prediction (average of 4 GMMs) and synthetic simulations as a function of period for the collection of 6 modeling groups. Each dashed line indicates one simulation with a bold line being the average of a modeler's simulations for Mw 7 ruptures.