HILLSLOPE DEVELOPMENT IN AREAS OF ACTIVE TECTONICS

Tectonic and geomorphic displacements of the Earth's surface control t opographic profile development; therefore, their analysis should be co mbined. In the model presented here, transient finite difference solut ions to the continuity equation for material transport determine geomo rphic displacements. The material transport rate is a function of dist ance from the divide to the power m, local slope to the power n, and a rate constant. Values of rn and n may be adjusted to simulate process es 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 so il profile development. Superimposed edge dislocations in an elastic h alf-plane are used to model tectonic displacements. Slip along a norma l or reverse fault of any dip, depth and down-dip length may be increm ental (earthquake) or continuous (aseismic creep). Considering climate and material properties constant, the ratio of the transport capacity rate constant to the fault slip rate roughly determines form. This mo del extends existing morphologic diffusion erosion analyses to include other geomorphic conditions and processes (transport- or weathering-l imited conditions, material flux boundary conditions, and the developm ent of gullies and knickpoints) and more heterogeneous spatial and tem poral distributions of tectonic displacement (such as those due to sli p along buried thrust faults). We advocate calibration of these parame ters and processes to provide a quantitative approach to modeling land form development, determining deformation rates, and inferring earthqu ake hazards.