Aecom Technical Services, Inc.

Project Title: Incorporating Rupture Directivity Effects Into Probabilistic Seismic Hazard Analyses for the NSHM: Dip-slip Faulting Earthquakes and Hypocenter Location Probability Distributionsproject Period: 1 1 2025 Through 12 31 2025AWARD Purpose: This Study Will Address an Important Need by Providing Updated Models for Predicting the Effects of Rupture Directivity on Earthquake Ground Motions. a Rupture Directivity Adjustment Model Canbe Applied to a Traditional Ground Motion Model (one Without Explicit Treatment of Rupturedirectivity) to Incorporate the Effects of This Phenomenon. Rupture Directivity Effects on Near-fault Ground Motions Are Known to Be Significant and Should Be Included to Accurately Estimate the Seismic Hazard, However, These Effects Are Not Explicitly Accounted for in Typical Ground Motion Models, and Therefore Not in Typical Probabilistic Seismic Hazard Analyses. Directivity Models Have Not Yet Been Widely Adopted in Practice Because of Theirrelative Complexity and the Uncertainty About How to Use Them. in Our Prior Usgs Final Technical Report (G22AP00199 Paper in Review at Earthquake Spectra), We Addressed These Issues by Developing a Rupture Directivity Model for Strike-slip Earthquakes Which Is Straightforward to Implement, and by Providing Instructions for Its Use in Seismic Hazard Analyses. the Proposed Study Is a Continuation of That Work, and We Will Provide a Rupture Directivity Adjustment Model for Dip-slip Faulting Earthquakes, Along With Probability Distribution Functions for the Hypocenter Location Within the Rupture Area in Future Earthquakes. These Components, Along With the Strikeslip Model From G22AP00199, Will Form a Comprehensive Rupture Directivity Model Applicable to Future Seismic Hazard Analyses Such as the Usgs National Seismic Hazard Model (nshm).activities to Be Performed: This Study Will Involve Two Main Components. the First Is to Develop a Rupture Directivity Adjustment Model for Dip-slip Faulting Earthquakes. This Model Will Be Derived Using Similar Techniques as the G22AP00199 Strike-slip Model, Including Residual Analyses of Earthquake Ground Motion Simulations and Recordings. the Directivity Model Will Provide Adjustments to Both the Median and Aleatory Variability of the Ground Motion Model. the Second Component Is to Study the Distributions of Earthquake Hypocenter Locations Within the Rupture Area This Will Be Performed Using a Database of Published Finite Fault Model Inversions and Using a Simulated Earthquake Catalog. Models for the Hypocenter Location Probability Distributions Are Needed for Forward Application of the Directivity Model Because the Directivity Model Relies on the Hypocenter Location,and Hypocenter Locations for Future Earthquakes Are Unknown.deliverables and Expected Outcomes: the Primary Deliverable Will Be a Directivity Model for Dip-slip Faulting Crustal Earthquakes, Including Computer Codes. We Will Provide Guidance on Implementation of the New Model,covering Deterministic and Probabilistic Seismic Hazard Applications With Examples, Treatment of Multi-segment Ruptures, and Recommended Hypocenter Location Probability Distributions. This Model Can Be Used in Future Seismic Hazard Applications, Including the Nshm.intended Beneficiaries: These Products Will Be Beneficial to Seismic Hazard Analysts and Engineers, Including Those Who Work on the Usgs NSHM. We Have Communicated With the Usgs and Will Collaborate With Kylewithers (letter of Commitment Attached) to Test and Implement the Model in the Usgs National Hazard Mapping Procedures. More on This Collaboration Is in Section B.4.2 (project Plan).subrecipient Activities: None