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Dependence of rupture nucleation and propagation on fluid injection rate: effective stress vs. variations in friction properties

maryam alghannam, Stacy Larochelle, Nadia Lapusta, Vito Rubino, Krittanon Sirorattanakul, Attilio Lattanzi, & Ares Rosakis

Submitted September 10, 2023, SCEC Contribution #13104, 2023 SCEC Annual Meeting Poster #211

Understanding the influence of fluid pressure on friction and fault stability is essential in efforts to mitigate the seismic risk associated with subsurface operations. Recent frictional sliding experiments on PMMA surfaces by Gori et al. (2021) show that, in cases of rapid increase in pore pressure, unstable, fast slip is promoted nearly instantaneously and for rupture lengths considerably smaller than the critical sizes predicted by quasistatic theoretical estimates. In cases of gradual pore pressure increase, dynamic slip is triggered from larger scales and at higher levels of injection fluid pore pressure. The study also finds that the resulting dynamic ruptures over wetted interfaces exhibit dynamic stress drops almost twice as large as those over dry interfaces. The underlying mechanisms behind these effects are unclear.

Here, we perform numerical simulations of the laboratory experiments using rate-and-state friction. In the case of rapid increase in pore pressure and the associated small fluid diffusion distance, fault slip is controlled by dry friction properties, while in the case of gradual pore pressure increase and the associated large diffusion distance, fault slip is largely controlled by the wet friction properties. However, the effective normal stress evolution and the associated quasi-static initial slip is also different in the two cases. Our simulations that resolve both slow and fast slip indicate that the difference between the two experiments cannot be explained by the different effective stress evolution alone. We will report on our current work to determine the range of changes in friction properties that provide a match to the experimental results. These findings, as a whole, indicate that the concept of effective stress may be insufficient to describe frictional interfaces in the presence of fluids, with friction properties themselves dependent on fluid presence and its properties.

alghannam, m., Larochelle, S., Lapusta, N., Rubino, V., Sirorattanakul, K., Lattanzi, A., & Rosakis, A. (2023, 09). Dependence of rupture nucleation and propagation on fluid injection rate: effective stress vs. variations in friction properties. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Computational Science (CS)