UCLA

The 50 state update to the 2023 United States National Seismic Hazard Model (NSHM) is the latest in a sequence published by the U. S. Geological Survey (USGS). The 2023 NSHM is intended for use in building codes and similar applications at return periods of 475 years (corresponding to exceedance probabilities of 10% in 50 years) or longer. In reviewing the model, the NSHM Program Steering Committee, consisting of the authors of this paper, considered the characteristics of “best available science” that are applicable to the NSHM. Best available science must perform better than the previous NSHM, and there should be no available alternatives that could improve the models. The following are suggested characteristics of “best available science”: A) Clear objectives B) Rigorous conceptual model C) Timely, relevant and inclusive D) Verified and reproducible E) Validated intermediate and final models F) Replicable within uncertainties G) Peer reviewed H) Permanent documentation This article focuses on the justification for, and intent of, the above criteria for best available science.