Using a dataset of preexisting mapped landslides, we create two maps that provide a firstorder approximation of rockfall susceptibility for the state of New Mexico. In natural hazard assessments, the term 'susceptibility' is used to describe the natural propensity of the landscape to produce a given hazard (in this case, rockfall). In other words, these maps depict the likelihood that a rockfall event will occur in a specified area based on local terrain conditions, given adequate driving forces or destabilizing phenomena.
For the purpose of our analyses, we include rock topples with rock falls. Both phenomena occur when a mass of rock fails on a very steep slope, cliff, or ledge. A period of free-fall may be involved initially, but most of the downslope transport involves bouncing and flying along ballistic trajectories or rolling down a slope (run-out zone). During this process, the rock mass may split into several pieces or evolve into a rock avalanche. Eventually, frictional forces will cause the rolling rock to come at rest, either on a slope or relatively gentle ground.