When and where does aseismic creep stop rupture propagation?

Julian C. Lozos

Published September 8, 2024, SCEC Contribution #13983, 2024 SCEC Annual Meeting Poster #154

Aseismic creep on faults is characterized by rate-strengthening friction, which means that the fault actively resists movement as slip rates increase. This resistance to coseismic rupture velocities approaching from adjacent locked fault sections suggests that the frictional behaviors associated with creep can, in and of themselves, be barriers to rupture. But because creeping sections of faults are in motion during the interseismic period, they also consistently release at least some portion of the shear stress imparted by tectonic loading. This may mean that creeping areas also have low enough shear stress to cause a rupture front to die out, even independently of their frictional conditions. Thus, understanding which combinations of frictional resistance and shear stress retention, over what length of fault patch, are able to stop versus allow throughgoing coseismic rupture is critical for evaluating hazard associated with partially-creeping faults. Here, I conduct a suite of dynamic rupture simulations on partially-creeping strike-slip faults under a range of stress conditions, varying frictional resistance and stress release in creeping patches of different lengths, and looking at the length and amount of surface slip of the resulting earthquake. My results so far are unsurprising: creeping areas that are longer, have more stress release due to creep, and have stronger frictional resistance are more likely to prevent rupture from reaching the end of the fault. More energetic ruptures are also able to overcome larger and more resistant creeping patches. My eventual goal, however, is to explore how this balance of factors affects whether or not rupture propagates past a creeping patch over a wide enough range of parameter space that I can develop a set of physics-based passing probabilities for partially-creeping faults. These probabilities will be useful for a range of applications, including interpreting geologic/paleoseismic evidence of past ruptures, probabilistic rupture forecasting, and source scenario development for both probabilistic and deterministic hazard modeling.

Key Words
aseismic creep, creep, rupture dynamics, rupture simulations, parameter study, fault friction, numerical modeling

Citation
Lozos, J. C. (2024, 09). When and where does aseismic creep stop rupture propagation?. Poster Presentation at 2024 SCEC Annual Meeting.

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