Open Seismic Risk Assessment Tool
The Pacific Earthquake Engineering Research (PEER) center in conjunction with the Lawrence Berkeley National Laboratory (LBNL), the SimCenter at Berkeley, and Slate Geotechnical Consultants and its subcontractors Lettis Consultants International (LCI), G&E Engineering Systems (G&E: J. Eidinger), Thomas O’Rourke, and GEOVision Geophysical Services is conducting a study to develop an open-source seismic risk assessment tool, called OpenSRA. The probabilistic seismic risk tool developed in this project will follow the widely accepted risk methodology of Dr. A. Cornell. A seismic source characterization is used to develop a suite of earthquake scenarios with associated rates of occurrence to represent the seismic hazard. Fault ruptures and the resulting ground deformation are generated for each earthquake scenario to represent the seismic loading, which includes a map of ground motion parameters. This scenario-based seismic parameter map is overlaid on the infrastructure system and the seismic loading combined with the capacities of the infrastructure to calculate the seismic performance of the natural gas system for the scenario. By repeating the process for all the scenarios in the suite the tool can evaluate the seismic risk to the system. Targeted research is also being performed to improve the characterization of uncertainty of key inputs to the seismic risk assessment tool. A user-driven research approach is being used with the primary objective of creating an open-source seismic risk tool (OpenSRA) for natural gas infrastructure that will be easily usable by regulators and utilities and which includes updated models and methods for the seismic demands and capacities that control the seismic risk for natural gas systems. The project includes several innovative approaches that will improve on the basic methodology and distinguish our approach from standard approaches currently used. Current risk studies developed by the utilities use risk scoring approaches that are highly subjective and qualitative. They do not properly incorporate the uncertainties in the seismic demand and in the fragility of the system and its components. The seismic risk methodology employed in this project provides quantitative estimates of the probabilistic seismic risk. For risk- informed decision-making processes the reliability of the risk estimates needs to be considered as this can be significant, particularly for large rare earthquakes.