Aecom Technical Services, Inc.

Plain Language Description Award Purpose: the Effects of Rupture Directivity on Near-fault Ground Motions Are Known to Be Significant and Should Be Included to Accurately Estimate the Hazard From Long Period Ground Motions (abrahamson, 2000). However, These Effects Are Not Explicitly Accounted for in Typical Ground Motions Models, and Therefore Not in Typical Probabilistic Seismic Hazard Analyses (PSHAS) Because Substantial Confusion Exists in Practice About Which Directivity Models to Use and How to Apply Them, Especially to Complex Multi-segment Rupture Models (donahue Et Al., 2019). in the Proposed Work, We Will Build Upon Our Rupture Directivity Model Previously Developed Under Usgs Award G18AP00092 (BEA20). the Result Will Be a Comprehensive Model Suitable for Use in Future Pshas, Including Those Performed as Part of the Usgs National Seismic Hazard Model.activities to Be Performed We Will Test and Refine BEA20 and Provide Recommendations for Using This Model in Seismic Hazard Analyses: First, We Will Investigate the Impact of the Model on the Total Aleatory Variability in Psha, Which Is Implicitly Increased Relative to a Non-directive Psha Due to Integration Over Multiple Hypocenter Locations. Next, We Will Test and Provide Guidance for Applying the Model to Complex Earthquake Source Descriptions. Finally, We Will Make Recommendations for Incorporating the Model Into Seismic Hazard Codes, Both for Site-specific Studies and the National Seismic Hazard Model. in Addition to These Guidelines, We Will Provide a Series of Psha Examples, Including Directivity Model Comparisons and Ground-motion Sensitivities. We Will Begin With Very Simple Source Description Examples and Gradually Increase in Complexity, Concluding With Example Utilizations of Complex Multi-segment Scenario Earthquakes in UCERF3 (field Et Al., 2013).DELIVERABLES and Expected Outcomes the Complete Directivity Model Will Include Formalized Instructions for Use in Psha, Including: - the Median Ground Motion Adjustment - the Aleatory Variability Adjustment - Hypocenter Location Distributions - Code Implementation Into the Open-source Hazard Software HAZ45 (hale Et Al., 2018) We Will Develop a Technical Report Summarizing These and Will Prepare a Manuscript for a Peer-reviewed Journal Based Jointly on This Report and the Final Technical Report From Award G18AP00092. the Results of This Project Will Be Beneficial to a Wide Range of Practicing Hazard Analysts, and to the Usgs for the National Seismic Hazard Mapping Project. We Have Communicated With the Usgs and Will Work Closely With Kyle Withers and Morgan Moschetti to Implement the Model in the Usgs National Hazard Mapping Workflow.subrecipient Activities No Subcontractors Are Involved in This Project