WGCEP: Working Group on California Earthquake Probabilities


An Earthquake Rupture Forecasts (ERF) gives the probability of all damaging earthquakes (e.g., Magnitude>5) throughout a region, over a specified time span, and at some level of discretization (or approximation).

The purpose of this Working Group is to develop statewide, time-dependent ERFs for California that use best available science and are endorsed by the United States Geological Survey (USGS), the Southern California Earthquake Center (SCEC), and the California Geological Survey (CGS). These models are referred to as the Uniform California Earthquake Rupture Forecasts (UCERFs).

Alternative UCERF versions are developed to incorporate improvements made over time, and to represent epistemic uncertainties at any given time. Therefore, another goal is to reach consensus that an adequate, minimum number of alternative models has been included (i.e., that span the range of viability and importance in terms of hazard or loss metrics of interest).

All activities in this Working Group are coordinated with the development of the USGS National Seismic Hazard Maps, and support has often been provided by the California Earthquake Authority, which has used our models in setting earthquake insurance rates.

The models are formally evaluated by a Scientific Review Panel, as well as by the California Earthquake Prediction Evaluation Council (CEPEC) and/or the National equivalent (NEPEC).

UCERFs are deployed in an adaptable and extensible model framework, using OpenSHA, whereby modifications can be made as warranted by scientific developments, the collection of new data, or following the occurrence of significant earthquakes (subject to a review process). Our implementation strategy is to add more advanced capabilities only after achieving more modest goals.

The models are tested via both traditional scientific analysis and through submission to the Collaboratory for the Study of Earthquake Predictability (CSEP).

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