Exciting news! We're transitioning to the Statewide California Earthquake Center. Our new website is under construction, but we'll continue using this website for SCEC business in the meantime. We're also archiving the Southern Center site to preserve its rich history. A new and improved platform is coming soon!

Stress Transfer and Seismic Clustering in Complex Fault Systems: Insights from 3-D Earthquake Simulations

Yi-Fan Yin

Submitted September 10, 2023, SCEC Contribution #13042, 2023 SCEC Annual Meeting Poster #126

Many recent earthquake sequences show how complex fault systems host clustered quakes of similar magnitudes. Clustered quakes can exacerbate the damaged buildings and add difficulty to hazard assessment based on isolated mainshocks. We know how earthquakes interact through stress transfer, but how likely does stress transfer promote large quakes in a fault system to cluster? In other words, how does stress transfer between faults affect the recurrence time and synchronization? Here, we present two numerical studies using earthquake cycle simulations in 3-D elastic half-space with multiple interacting faults slipping under rate-and-state friction law. The simulations generate long sequences with characters of natural catalogs.

In the first study, we simulated a generic *en echlon* fault system of three identical strike-slip faults. We extract the distributions of the recurrence time of a single fault as well as across the fault system from the long sequences over 100 events. Our result indicates that the chance of another mainshock nucleating right after one can be as high as 30% when the critical nucleation length is small, while the individual fault ruptures its full extent quasi-periodically. In all cases, the conditional expectancy resembles a Brownian-passage time distribution.

The second experiment consists of a more varies geometry. We simulate a system of ten normal faults using the first-order geometry and slip rates derived from the Central Apennines fault system. The fault planes remain rectangular and flat. With a range of fault sizes and slip rate, the system recurrence time resembles a Poissonian distribution, with a slight tendency of short-term clustering. Faults that involved in the L'Aquila sequence and Amatrice-Visso-Norcia sequence exhibit slightly higher short-term clustering tendencies compared to the system. The normal fault planes seen in the field and by aftershocks are much more complex and curved. Our result serves as the base case, while a more complex geometry would further alter the stress field and resulting seismic sequence.

Key Words
SEAS, recurrence time, fault interaction, numerical simulation

Yin, Y. (2023, 09). Stress Transfer and Seismic Clustering in Complex Fault Systems: Insights from 3-D Earthquake Simulations. Poster Presentation at 2023 SCEC Annual Meeting.

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