Morphotectonic Evolution of an Alluvial Fan: Results of a Joint Analog and Numerical Modeling Approach

Abstract

Surface topography results from complex couplings and feedbacks between tectonics and surface processes. We combine analog and numerical modeling, sharing similar geometry and boundary conditions, to assess the topographic evolution of an alluvial fan crossed by an active thrust fault. This joint approach allows the calibration of critical parameters constraining the river deposition–incision laws, such as the settling velocity of suspended sediments, the bed-rock erodibility, or the slope exponent. Comparing analog and numerical models reveals a slope-dependent threshold process, where a critical slope of ca. 0.081 controls the temporal evolution of the drainage network. We only evidence minor topographic differences between stable and stick-slip fault behavior localized along the fault scarp. Although this topographic signature may increase with the slip rate and the return period of slip events, it remains slight compared to the cumulated displacement along the fault scarp. Our results demonstrate that the study of morphology cannot be used alone to study the slip mode of active faults but can be a valuable tool complementing stratigraphic and geodetic observations. In contrast, we underline the significant signature of the distance between the fault and the sediment source, which controls the degree of channels incision and the density of the drainage network.

Sediment Recycling and the Evolution of Analog Orogenic Wedges

“…The analog material used in the models consists of a water‐saturated mixture of granular materials able to reproduce both brittle deformation and surface processes (Garcia‐Estève et al., 2021; Graveleau & Dominguez, 2008; Graveleau et al., 2011; Guerit et al., 2016; Reitano et al., 2020; Mao et al., 2021; Strak et al., 2011). The mixture is comprised of 40 wt.% of Silica Powder (SP), 40 wt.% of Glass Microbeads (GM), and 20 wt.% of PolyVinyl Chloride powder (PVC).…”

Revealing the hidden signature of fault slip history in the morphology of degrading scarps

“…Active faulting leaves a morphological signature that has been amply used in numerous studies to quantify active tectonics 9 . However, whether landscapes keep a record of how active faults slip, either seismically or aseismically, has remained largely unexplored 10,11 . With the increasing availability of high-resolution topographic data (<1 m resolution), there is a timely opportunity to investigate this issue 12 .…”