Enhancing  Fault Locking Estimations in the Hayward Fault Using a Metropolis-Hastings Boundary Element Method

Axel J. Periollat, & Gareth J. Funning

Published September 8, 2024, SCEC Contribution #13913, 2024 SCEC Annual Meeting Poster #144

Modeling the potential seismic hazard posed by faults requires accurate knowledge of where any locked asperities are and how fast the interseismic strain is accumulating on those asperities. Quantifying this strain is crucial for understanding earthquake nucleation and propagation. Geodetic observations (InSAR and GNSS) can provide constraints on both of these aspects; however such data can lack the spatial resolution that we desire, resulting in nonunique or poorly resolved models of fault locking.
One potential way to improve the resolution of such models is to include more physics. The Boundary Element Method (BEM) allows us to estimate the slip on fault surfaces where there is a combination of locking and aseismic slip (creep) in a mechanically consistent manner. Proximity to locked asperities can suppress the creep rate, for example, with potentially detectable consequences far from the asperity itself. To explore the utility of such models, we couple the BEM approach with a Metropolis-Hastings algorithm that samples different potential locking distributions, guided by the fit to geodetic data.
We test one case study of partially creeping fault, the Hayward fault, to test our approach. The abundant geodetic data available in the area can provide strong constraints on the fault locking models, while prior studies will help benchmark our results.
We will present our preliminary attempts to optimize our workflow, including reducing the computation time for each iteration of the BEM, and identifying patterns in the large array of potential locking distributions that we obtain, aiming for more realistic solutions.
We will investigate later other case studies and also the possibility of using the code for different phases of the earthquake cycle, and more realistic treatment of frictional behavior on our faults of interest.

Citation
Periollat, A. J., & Funning, G. J. (2024, 09). Enhancing  Fault Locking Estimations in the Hayward Fault Using a Metropolis-Hastings Boundary Element Method. Poster Presentation at 2024 SCEC Annual Meeting.

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