Hillslope sediment transport processes such as bioturbation, rainsplash, and granular mechanics occur across the entire planet. Yet, it remains uncertain how these small-scale processes act together to shape landscapes. Longstanding hillslope diffusion theory posits that hillslope processes are spatially limited, whereas new concepts of nonlocal sediment transport argue otherwise. However, each theory produces subtly different, but distinct, predictions for the evolution of fault scarps. We use the topographic change of fault scarps to demonstrate that hillslope processes produce nonlocal sediment transport. Analysis of a global compilation of 340 dated single-earthquake scarp profiles reveals a statistically significant (p < 0.05) relationship between scarp age and scarp asymmetry, here defined as the ratio of imaginary to real components of the Fourier transform of absolute slope. Numerical simulations show that nonlocal models predict this relationship, whereas hillslope diffusion models do not. To further investigate this result, we examined the depositional geometry of a well-exposed colluvial wedge along the Wasatch fault in central Utah, United States. Our quantitative comparison between the exposure and numerical simulations reveals better agreement with the nonlocal model. Nonlocal sediment transport theory appears to best capture the physics of how hillslope processes shape fault scarps, yet hillslope diffusion provides a useful approximation in many cases. As the processes that act on fault scarps are nearly identical to those acting on hillslopes, our results provide evidence supporting nonlocality as a generalized model of hillslope sediment transport.
Research Article|
January 17, 2025
Early Publication
Evidence for nonlocal sediment transport on hillslopes from fault scarp morphology
Harrison Gray;
Harrison Gray
1
U.S. Geological Survey, Geosciences and Environmental Change Science Center, Denver, Colorado 80225, USA
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Tyler Doane;
Tyler Doane
2
Desert Research Institute, Las Vegas, Nevada 89119, USA
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Sylvia Nicovich;
Sylvia Nicovich
3
U.S. Geological Survey, Geologic Hazards Science Center, Golden, Colorado 80401, USA
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Miriam Primus;
Miriam Primus
4
Warner College of Natural Resources, Colorado State University, Fort Collins, Colorado 80523, USA
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Christopher DuRoss;
Christopher DuRoss
3
U.S. Geological Survey, Geologic Hazards Science Center, Golden, Colorado 80401, USA
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Ryan Gold
Ryan Gold
3
U.S. Geological Survey, Geologic Hazards Science Center, Golden, Colorado 80401, USA
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Harrison Gray
1
U.S. Geological Survey, Geosciences and Environmental Change Science Center, Denver, Colorado 80225, USA
Tyler Doane
2
Desert Research Institute, Las Vegas, Nevada 89119, USA
Sylvia Nicovich
3
U.S. Geological Survey, Geologic Hazards Science Center, Golden, Colorado 80401, USA
Miriam Primus
4
Warner College of Natural Resources, Colorado State University, Fort Collins, Colorado 80523, USA
Christopher DuRoss
3
U.S. Geological Survey, Geologic Hazards Science Center, Golden, Colorado 80401, USA
Ryan Gold
3
U.S. Geological Survey, Geologic Hazards Science Center, Golden, Colorado 80401, USA
Publisher: Geological Society of America
Received:
27 Nov 2024
Accepted:
30 Dec 2024
First Online:
17 Jan 2025
Online ISSN: 1943-2682
Print ISSN: 0091-7613
© 2025 The Authors
Geology (2025)
Article history
Received:
27 Nov 2024
Accepted:
30 Dec 2024
First Online:
17 Jan 2025
Citation
Harrison Gray, Tyler Doane, Sylvia Nicovich, Miriam Primus, Christopher DuRoss, Ryan Gold; Evidence for nonlocal sediment transport on hillslopes from fault scarp morphology. Geology 2025; doi: https://doi.org/10.1130/G52987.1
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