Exploring the Effects of Higher Normal Stress and Lower Characteristic Slip Distance on Earthquake Behavior

Alexander R. Frank, Hassanat Ahmed, Mira Zedan, & Natalie Schaal

Submitted September 7, 2025, SCEC Contribution #14886, 2025 SCEC Annual Meeting Poster #TBD

Despite continuous advancements in understanding earthquake processes via improvements in sensing and computational technology, how earthquakes nucleate remains a fundamental question of earthquake science. Instability ratio, which is the ratio of the seismogenic fault length to the nucleation size, is considered to be a key parameter in influencing the sequence of events that occur on a given fault. However, the same nucleation size and, hence, the same instability ratio, can be theoretically achieved using different combinations of fault parameter values. Building off of previous work [e.g., Schaal and Lapusta, 2019], here we explore the influence of elevated normal stress or lowered characteristic slip distance on earthquake behavior for the same set of instability ratios. This exploration is within a rate-and-state frictional framework, simulating a 2D fault using the hybrid code of Abdelmeguid and Elbanna, 2022. We report on the effects of the frictional parameter cases on the simulated sequence of earthquakes, source parameters and any other characteristic features. Initial results indicate that the earthquakes produced on faults with lower characteristic slip distance are more frequent and less intense than those produced on faults with higher normal stress for the same instability ratio. This investigation of parameter influence in a homogeneous setting is a first step before adding the complexity of heterogeneity. This ongoing work fits within a longer-term project to compare the effects of on-fault heterogeneity (via frictional parameters) versus off-fault heterogeneity (via plasticity) on the sequence of events. We hope that this work will contribute to a deepened understanding of the relationship between fault parameters and earthquake behavior.

Key Words
Earthquake nucleation, Rate-and-state friction, Earthquake simulation, Modeling

Citation
Frank, A. R., Ahmed, H., Zedan, M., & Schaal, N. (2025, 09). Exploring the Effects of Higher Normal Stress and Lower Characteristic Slip Distance on Earthquake Behavior. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)