SCEC Award Number 22096 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Continued Development of OpenSHA to Support Next-Generation Earthquake Rupture Forecasts and Facilitate User Adoption
Name Organization
Christine Goulet University of Southern California Edward Field United States Geological Survey Kevin Milner University of Southern California
Other Participants
SCEC Priorities 4c, 4d, 5a SCEC Groups EFP, EEII, CS
Report Due Date 03/15/2023 Date Report Submitted 01/26/2024
Project Abstract
Development in 2022 was focused primarily on the 2023 update to the USGS National Seismic Hazard Model (NSHM23). The first complete draft model for the Western U.S. was made available to the scientific review panel on 9/28/2022. Development of this draft built upon preparations in prior years when we developed an updated methodology using UCERF3 ingredients. In 2022 we received and integrated inputs for the 2023 model including the geologic fault and deformation models, geodetic deformation models, and paleoseismic constraints.

Additionally, we computed the first RSQSim-CyberShake hazard map. Building upon prior prototype calculations, this was the first end-to-end physics-based PSHA map. Initial analysis indicates that the RSQSim-CyberShake model contains a similar amount of total ground motion variability as simpler empirical models, but lower variability for individual sites and sources can decrease hazard estimates even for sites where ground motions are higher on average.

We continued to support OpenSHA desktop applications, which were downloaded nearly 3,000 times in 2022.
Intellectual Merit The work described in this report helps achieve SCEC’s goal of integrating data and models into usable products that also support continued research. It improves upon previous approaches in multiple ways, including a more physically consistent set multi-fault ruptures, better inversion convergence and data fits than prior models, and better acknowledgement and sampling of model uncertainties. These innovations have been or will be published in peer-reviewed journals, as well as internally within the USGS.
Broader Impacts OpenSHA, and its implementation of the UCERF3 models, continues to be a valuable tool for the SCEC community. OpenSHA is used by engineers, researchers, and students, and was downloaded nearly 3,000 times in 2021.

The work on the 2023 update to the national seismic hazard model (NSHM23) will help to synthesize data from a number of different SCEC-funded projects (e.g., fault slip rate and paleoseismic studies) into useful and widely used models for the community.
Exemplary Figure Figure 1
Hazard maps for the preliminary model for the Western U.S., computed with the Abrahamson et al. (2014) ground motion model. Shown are ground motions with 2% probability of exceedance in 50 years. The top left large map shows hazard averaged across all logic tree branches. Each subpanel to the right panel shows hazard ratios (expressed as percent change) and differences for each logic tree branch choice. This is calculated by computing and then averaging hazard across a subset of the logic tree consisting of only branches including the given choice, and comparing that map to the total mean map. In total, 2,250 fault-based logic tree branches are considered, and are then combined with 54 gridded seismicity model branches. 50 million hazard curves were computed for this comparison at USC’s Center for Advanced Research Computing.