Tectonic and geomorphic displacements of the earth's surface control topographic profile development; therefore, their analysis should be combined. In the model presented here, transient finite difference solutions to the continuity equation for material transport determine geomorphic displacements. The material transport rate is a function of distance from the divide to the power m , local slope to the power n , and a rate constant. Values of m and n may be adjusted to simulate processes varying from rainsplash and soil creep (i.e., diffusive; m = 0, n = 1) to slope wash and river flow (m > 0, n > 0). The actual geomorphic displacements may be transport or weathering-limited, depending on soil profile development. Superimposed edge dislocations in an elastic half-plane are used to model tectonic displacements. Slip along a normal or reverse fault of any dip, depth and down-dip length may be incremental (earthquake) or continuous (aseismic creep). Faults of spatial scale much less than crustal thickness are considered, so isostatic responses to topographic loading are neglected. Profile development is modeled by identifying an initial profile shape and constant sediment flux or constant elevation boundary conditions, soil production and process parameters, age, and fault geometry and slip rate. Model tectonic landforms are sensitive to the ratio of geomorphic and tectonic displacement distributions in space and time. Considering climate and material properties constant, the ratio of the transport capacity rate constant to the fault slip rate roughly determines form. This model extends existing morphologic diffusion erosion analyses to include other geomorphic processes and more complex spatial and temporal distributions of tectonic displacement. Specific examples and conclusions include the following: 1) Fault scarp degradation is modeled due to transport- or weathering limited conditions. The curvature of the soil/bedrock interface may be preserved long after the topographic expression of a earthquake surface rupture is degraded. 2) Sediment flux boundary conditions permit the development of complicated profiles reflected about their boundaries. 3) We consider the diffusive development of fault scarps and their incision by surface wash processes and thus the formation of gullies and the development of knickpoints. 4) Fault scarps that form by continuous surface rupture will be relatively steeper and the curvature of their soil/bedrock interfaces will be greater than for scarps with the same total tectonic displacement from a single seismic event. 5) Active thrust faults that both rupture the surface and are blind are examined. The simulations serve to develop intuition, and to indicate which parameters or processes should be the focus of detailed field observations. We advocate calibration of these parameters and processes to provide a quantitative approach to modeling landform development, determining deformation rates, and inferring earthquake hazards.

(Continental tectonics, geomorphology, structural geology, erosion and sedimentation.)