Mountain ranges surrounding bends in strike-slip faults reveal fault strength

Curtis W. Baden, Johanna M. Nevitt, & George E. Hilley

Submitted September 10, 2023, SCEC Contribution #13249, 2023 SCEC Annual Meeting Poster #147

Frictional fault strength limits the accumulation of stress in the surrounding crust, but this strength is difficult to measure along natural fault systems. Around contractional bends in strike-slip faults, or restraining bends, the concentration of stress and resultant deformation surrounding the bend in the fault varies as a function of strike-slip fault frictional strength and restraining bend angle. Restraining bends may thus serve as long-term natural experiments, in which deformation that develops adjacent to these features and accumulates over millions of years may reveal a fault’s long term frictional strength. To test this idea, we modeled deformation and rock uplift surrounding restraining bends along strike-slip faults with a set of generalized finite element models, in which we varied the restraining bend angle and the coefficient of static friction along the fault. We find that the frictional strength of faults controls rock uplift distributions surrounding restraining bends. Whereas weak faults allow crust to be advected into and through modeled bends, strong faults impound rock uplift within and ‘upwind’ of the restraining bend, such that bend-induced rock uplift propagates away from the restraining bend in a direction opposite to that of relative strike-slip fault motion. We use the trends observed in our models to infer fault frictional strength along major strike-slip and transform fault strands for natural restraining bend systems around the world. Where present, prior estimates of frictional fault strength for these natural structures are consistent with model-informed inferences of frictional strength based on field observations. Our study indicates that geologic expressions of deformation around these restraining bends may be useful in constraining fault strength.

Key Words
restraining bend, friction, fault strength

Citation
Baden, C. W., Nevitt, J. M., & Hilley, G. E. (2023, 09). Mountain ranges surrounding bends in strike-slip faults reveal fault strength. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Stress and Deformation Over Time (SDOT)