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The Collaboratory for the Study of Earthquake Predictability (CSEP) is a global cyberinfrastructure for prospective evaluations of earthquake forecast models and prediction algorithms. CSEP's goals are to improve our understanding of earthquake predictability, advance forecasting model development, test key scientific hypotheses and their predictive power, and to improve seismic hazard assessments. Since its inception in California in 2007, the global CSEP collaboration has been conducting forecast experiments in a variety of tectonic settings and at the global scale, and now operates four testing centers on four continents to automatically and objectively evaluate models against prospective data. These experiments have provided a multitude of results that are informing operational earthquake forecasting systems and seismic hazard models, and they have provided new, and sometimes surprising, insights into the predictability of earthquakes and spurned model improvements. CSEP has also conducted pilot studies to evaluate ground-motion and hazard models. Here, we report on selected achievements from a decade of CSEP, and we present our priorities for future activities.

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The Global Earthquake Activity Rate (GEAR1) seismicity model uses an optimized combination of geodetic strain rates, hypotheses about converting strain rates to seismicity rates from plate tectonics, and earthquake-catalog data to estimate global m w ≥ 5.767 shallow (≤ 70 km) seismicity rates. It comprises two parent models: a strain rate-based model, and a smoothed-seismicity based model. The GEAR1 model was retrospectively evaluated and calibrated using earthquake data from 2005-2012, resulting in a preferred log-linear, multiplicative combination of the parent forecasts. Since October 1, 2015, the GEAR1 model has undergone prospective evaluation within the Collaboratory for the Study of Earthquake Predictability (CSEP) testing center. We present initial prospective forecast test results for the GEAR1 model, its tectonic and seismicity components, and for the first iteration of the strain rate-based model, during the period October 1, 2015 to September 7, 2017. Observed earthquakes are consistent with the GEAR1 forecast, supporting a near-even contribution from geodetic strain rates and smoothed seismicity in constraining long-term global shallow earthquake rates. Comparative test results likewise support 1 2 that GEAR1 is more informative than either of its components alone. The tectonic forecasts do not effectively anticipate observed spatial earthquake distribution, largely due to intraplate earthquakes and a higher-than-implied degree of spatial earthquake clustering.