SCEC Award Number 20118 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Continued Development of OpenSHA/UCERFs in Support of OEF, Physics-Based Hazard Assessment, and Loss Modeling
Investigator(s)
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 CS, EFP, EEII
Report Due Date 03/15/2021 Date Report Submitted 03/30/2021
Project Abstract
 Development in 2020 was focused on physics-based probabilistic seismic hazard analysis (PSHA), improving access to OpenSHA applications, and multi-fault rupture plausibility for the next Uniform California Earthquake Rupture Forecast (UCERF) model. The RSQSim-CyberShake model is the first of it’s kind that combines a deterministic full-cycle physics-based earthquake simulator with physics-based ground motion simulations to perform fully nonergodic PSHA calculations. This achievement was made possible by building upon work from prior reporting years, and was recently published (Milner et al., 2021).

We launched a new OpenSHA website in 2020 with improved documentation (www.opensha.org). The new website is based on a wiki allowing for easy updating, and replaces an outdated drupal website that had become uneditable. We also formally re-released our applications on GitHub and started nightly builds of the applications and libraries from the git repositories.

Work has begun on the 2023 update to the USGS National Seismic Hazard Model. For this update, we will extend the UCERF3 methodology to the entire western US. Significant progress has been made on improving the plausibility filtering process by which the set of allowed multi-fault ruptures are determined. UCERF3 relied on simple azimuth change rules that are best suited for purely right-lateral fault systems. We have developed new filters using Coulomb stress transfer that improve upon the UCERF3 methodology and add more connectivity to the model.

We also made improvements to the UCERF3 Epidemic Type Aftershock Sequence (UCERF3-ETAS) model and continued to run the model after any M≥5 event in California.
Intellectual Merit One of the three bullets in SCEC’s mission statement is to “Integrate information into a comprehensive, physics-based understanding of earthquake phenomena.” To that end, we developed the first probabilistic seismic hazard study using exclusively three-dimensional, physics-base models (RSQSim and CyberShake) in this reporting period. This has been published in Milner et al. (2021).
Broader Impacts OpenSHA, and it’s implementation of the UCERF3 models, continues to be a valuable tool for the SCEC community. OpenSHA is used by engineers, researchers, and students. Our new website and improved application build process improves access to these models for the broader community. OpenSHA is also used in conjunction with CyberShake to generate seismic hazard maps and to generate data products for the UGMS project, which includes a public facing design response spectra tool for engineers (https://data2.scec.org/ugms-mcerGM-tool_v18.4/).
Exemplary Figure Figure 1
3D perspective view (looking north) of a complex synthetic M 7.8 RSQSim rupture in the Los Angeles basin. The rupture nucleates on the Compton fault and then spreads to the Newport–Inglewood, Palos Verdes, and other nearby faults. In total, 10 different UCERF3 fault sections participate, but the three aforementioned faults account for greater than 90% of the total seismic moment. Darker colors represent patches of larger total cumulative slip, and participating faults are labeled (the Elysian Park and San Pedro Basin faults also participate but are omitted as their contributions to the total seismic moment released are negligible).
Credit: from Milner et al. (2021)
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