SCEC Award Number 22035 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Evolution of ground motion characteristics over earthquake cycle timescales
Investigator(s)
Name Organization
Dunyu Liu University of Texas at Austin Christine Goulet University of Southern California Yongfei Wang University of Southern California
Other Participants
SCEC Priorities 4a, 2e, 4c SCEC Groups GM, FARM, SDOT
Report Due Date 03/15/2023 Date Report Submitted 03/15/2024
Project Abstract
 Dynamic rupture models provide a critical link between earthquake physics, fault structure, and ground motion. Computations are particularly valuable to assess near-fault broadband ground motions affected by source physics, a critical area of interest in seismic hazard, but poorly represented in empirical datasets. However, such applications suffer from significant uncertainties associated with pre-event assumptions, notably for the initial stress conditions. These initial stress conditions are partially inherited from earlier surrounding earthquakes, meaning that the variability inherent to rupture processes and resulting ground motions may depend on the earthquake sequence history. We developed an open-source Earthquake System Coupling Infrastructure to support dynamic rupture code and earthquake cycle code. We simulated an earthquake sequence on a structurally rough strike-slip fault. Preliminary results show that stresses change significantly after each earthquake. The temporal evolutions of stress, frictional, and kinetic states affect rupture dynamics and correspondent ground motion characteristics. It challenges currently common practice of adopting relatively homogeneous initial conditions for single dynamic rupture applications.
Intellectual Merit The research promotes open-source parallel computing codes and infrastructure that allows physics-based earthquake cycles that can address ground motion with dynamic ruptures. It aligns with SCEC’s practical concerns with earthquake ground motion and theoretical objective to understand earthquake behavior as a system. Research on temporal evolution of earthquake source dynamics and ground motion is still in its early stage.
Broader Impacts The research supports two early career scientists. In addition, the open-source computing software for earthquake dynamic ruptures and cycles contain testing and examples that could be used in teaching and training future computational seismologists.
Exemplary Figure Figure 1. Framework and pathways for EQsimu, the Earthquake System Coupling Infrastructure. EQquasi, the earthquake cycle module simulates earthquake phases of post-seismic, inter-seismic, and nucleation, and pass initial stress and frictional states to EQdyna, the dynamic rupture module. Ground motion could be generated in dynamic ruptures. The updated stress and frictional fields will be passed back to EQquasi for the next earthquake cycle. The process will be repeated for earthquake sequence. Traditional ground motion simulations with dynamic ruptures rely on rule-based initial conditions (black dashed arrows). EQsimu allows two-way interactions between dynamic ruptures and non-dynamic-rupture phases.

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