Incorporating and reporting uncertainties in fault slip rates

Quantitative slip rate estimates are essential to understanding crustal deformation processes and assessing seismic hazard. Computing slip rates requires two fundamental ingredients: estimates of the age of an offset landform or deposit and displacement along the fault of interest. Because both of these measures contain uncertainty, slip rates are inherently uncertain. Methods to compute and report slip rates have not been standardized, and therefore slip rate data are presented inconsistently and are frequently ambiguous; in particular, slip rate uncertainty is often insufficiently characterized. We present a rigorous probabilistic approach to computing and reporting intermediate- to long-term fault slip rates; additionally, we have developed freely available software that provides standard age and displacement uncertainty models. We demonstrate the method using recent observations from the Neodani and Death Valley-Fish Lake Valley fault zones, and we compare slip rates determined using this approach with previously published results.