Evaluation of ETAS and STEP Forecasting Models for California Seismicity Using Point Process Residuals

Variants of the Epidemic-Type Aftershock Sequence (ETAS) and Short-Term Earthquake Probabilities (STEP) models have been used for earthquake forecasting and are entered as forecast models in the purely prospective Collaboratory Study for Earthquake Predictability (CSEP) experiment. Previous analyses have suggested the ETAS model offered the best forecast skill for the first several years of CSEP. Here, we evaluate the prospective forecasting ability of the ETAS and STEP one-day forecast models for California from 2013 to 2017, using super-thinned residuals and Voronoi residuals. We find very comparable performance of the two models, with slightly superior performance of the STEP model compared to ETAS according to most metrics.