Alex Hatem, USGS

Geologic slip rates represent time-averaged fault displacement and are a handy metric to define a fault’s activity. Useful as they are, slip rates aggregate numerous earthquakes that have occurred between field-based observation points, which are typically dated offset geomorphic features (e.g. stream channels or terrace risers). This means that time-displacement paths - that is, the potentially erratic stick-slip journeys of displacement-time pairs between geomorphic features - are usually unknown.

Here, I present a field study of incremental geologic slip rates along the Hope fault (Marlborough fault system, New Zealand), discuss some pitfalls of geologic slip rates as a metric, and present a potential path forward toward quantifying variability when we calculate geologic slip rates. The numerical approach presented (STEPS) is a complement to geologic field observations and is a data-driven method to provide reasonable estimates of fault time-displacement histories between field measurements.