Along coastal California, the possibility of earthquakes and landslides are commonly prefaced by the phrase, “not if, but when.” This precarious reality is now a bit more predictable thanks to researchers at UC Santa Cruz and The University of Texas at Austin, who found that conditions known to cause slip along fault lines deep underground also lead to landslides above. The new study, led by UC Santa Cruz geologist Noah Finnegan, used detailed data from two landslide sites in Northern California that researchers have identified and closely monitored for years. Finnegan and his co-author then applied a model originally developed to explain slow fault slip and eventually landed on a striking result: The model worked just as well for landslides as it did for faults. The finding is an important breakthrough suggesting that a model designed for faults can also be used to predict landslide behavior. And in California, where slow-moving slides are constant and cost hundreds of millions of dollars annually, this represents a major step forward in the ability to predict landslide movements—particularly in response to environmental factors like changes in groundwater levels.