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. Most landscape evolution models adopt the paradigm of constant anduniform uplift. It results that the role of fault activity and earthquakeson landscape building is understood under simplistic boundary conditions.Here, we develop a numerical model to investigate river profile developmentsubjected to fault displacement by earthquakes and erosion. The modelgenerates earthquakes, including mainshocks and aftershocks, that respectthe classical scaling laws observed for earthquakes. The distribution ofseismic and aseismic slip can be partitioned following a spatialdistribution of mainshocks along the fault plane. Slope patches, such asknickpoints, induced by fault slip are then migrated at a constant rateupstream a river crossing the fault. A major result is that this new modelpredicts a uniform distribution of earthquake magnitude rupturing a riverthat crosses a fault trace and in turn a negative exponential distributionof knickpoint height for a fully coupled fault, i.e. with only co-seismicslip. Increasing aseismic slip at shallow depths, and decreasing shallowseismicity, censors the magnitude range of earthquakes cutting the rivertowards large magnitudes and leads to less frequent but higher-amplitudeknickpoints, on average. Inter-knickpoint distance or time betweensuccessive knickpoints follows an exponential decay law. Using classical rates for fault slip (15 mm year −1 ) and knickpointretreat (0.1 m year −1 ) leads to high spatial densities of knickpoints. Wefind that knickpoint detectability, relatively to the resolution oftopographic data, decreases with river slope that is equal to the ratiobetween fault slip rate and knickpoint retreat rate. Vertical detectabilityis only defined by the precision of the topographic data that sets the lowermagnitude leading to a discernible offset. Considering a retreat rate with adependency on knickpoint height leads to the merging of small knickpointsinto larger ones and larger than the maximum offset produced by individualearthquakes. Moreover, considering simple scenarios of fault burial byintermittent sediment cover, driven by climatic changes or linked toearthquake occurrence, leads to knickpoint distributions and river profilesmarkedly different from the case with no sediment cover. This highlights thepotential role of sediments in modulating and potentially altering theexpression of tectonic activity in river profiles and surface topography.The correlation between the topographic profiles of successive parallelrivers cutting the fault remains positive for distance along the fault ofless than half the maximum earthquake rupture length. This suggests thatriver topography can be used for paleo-seismological analysis and to assessfault slip partitioning between aseismic and seismic slip. Lastly, thedeveloped model can be coupled to more sophisticated landscape evolutionmodels to investigate the role of earthquakes on landscape dynamics.

Statistical modelling of co-seismic knickpoint formation and river response to fault slip