Task Description – This research program aims to provide fault displacement hazard input for seismic risk assessment for OpenSRA. There are a variety of methodologies that may be used to quantify fault displacement hazard that range from extremely simple to complex. The methodologies and information were split into categories to assess fault displacement at a state-wide, a regional, and a site specific scale. With this in mind, fault geometries (location etc.) and characteristics (potential magnitude) were compiled using publicly available datasets developed by the California Geological Survey (CGS) and US Geological Survey (USGS). These include the Unified California Earthquake Rupture Forecast, Version 3 (UCERF3) (Field et al., 2013), the latest version of the U. S. Quaternary Fault, and Fold Database (Q-faults) (USGS and CGS, 2019), and allowing for site-specific information to be integrated into the analyses when available. These faults were then mapped to predict pipeline crossings and uncertainty bounds estimated regarding location and slip direction. Finally available fault displacement models were compiled and used to calculate potential displacement at each of these crossings. This information was then used to aid in fragility development for buried pipelines, wells, and caprocks.
Overall, this team:
Located where active tectonic faults intersect California’s natural gas infrastructure;
Described the earthquake magnitudes and rates that are expected to occur on the intersecting faults;
Summarized and/or developed relationships between the earthquakes that occur and the resulting amount of fault displacement at a given location;
Predicted the expected direction of fault displacement; and
Summarized additional geotechnical parameters that may be utilized by OpenSRA for fragility assessment –these include a description of the rupture width (width over which the fault displacement will occur) and strength properties of the soil or rock surrounding buried facilities.
Lead Investigator: Steve Thompson (Lettis Consultants International, LCI)
Team Members: Norm Abrahamson (University of California, Berkeley), Alodie Bubeck (LCI)