Project Grant G25AP00369

PROJECT TITLE: GEOSPATIAL AND GEOLOGIC SITE TERMS FOR NONERGODIC GROUND MOTION MODELS FOR CALIFORNIA AND UTAH:COLLABORATIVE RESEARCH WITH TUFTS UNIVERSITY AND MERRIMACK COLLEGEPROJECT PERIOD: 8 1 2025 THROUGH 7 31 2026AWARD PURPOSE: EARTHQUAKE GROUND-MOTION MODELS (GMMS) ARE A CRITICAL COMPONENT OF SEISMIC HAZARD ASSESSMENT. IN ORDER TO ACHIEVE MORE ACCURATE MODELING OF SITE EFFECTS IN GMMS THAT ARE BOTH INFORMATIVE OF GEOLOGIC CONDITIONS AND SPATIALLY CONTINUOUS (I.E., ABLE TO BE MEASURED AT ANY LOCATION WITHIN THE MODELED AREA), WE PROPOSE A PARADIGM SHIFT FOR GROUND-MOTION MODELING. INSTEAD OF FOCUSING THE DEVELOPMENT OF GMM SITE TERMS ON SITE-SPECIFIC VELOCITY PROFILES THAT ARE NOT UNIVERSALLY AVAILABLE, THE RECIPIENT HYPOTHESIZE THAT INCORPORATING BROADLY-AVAILABLE GEOSPATIAL AND GEOLOGICAL DATA BEFORE SITE-SPECIFIC SEISMIC VELOCITIES WILL LEAD TO IMPROVEMENTS IN SITE-TO-SITE RESIDUALS IN GMMS. THE OBJECTIVE OF THIS STUDY IS TO DEVELOP A SPATIALLY-CONTINUOUS SITE EFFECTS MODEL FOR GMMS FOR CALIFORNIA AND UTAH THAT CAN BE UPDATED WITH SITE-SPECIFIC DATA, ALLOWING FOR IMPROVED AND INCLUSIVE RISK ESTIMATION. THE SPATIALLY CONTINUOUS DATA WILL BE DERIVED FROM DIGITAL ELEVATION MODELS AND SURFICIAL GEOLOGY MAPS FOR EACH STATE. THE FUNDAMENTAL PARAMETERS OF THE GMM SITE TERMS WILL INVOLVE GEOSPATIAL PARAMETERS AND REGIONAL GEOLOGY, AND OUR FRAMEWORK WILL ALLOW FOR THE GMM TO BE UPDATED WITH SITE-SPECIFIC GEOTECHNICAL DATA WHERE IT IS AVAILABLE.ACTIVITIES TO BE PERFORMED: THE ACTIVITIES TO BE PERFORMED INCLUDE: (1) DEVELOP A SPATIALLY-CONTINUOUS NONERGODIC SITE TERM FOR GMMS IN CALIFORNIA USING GEOSPATIAL VARIABLES AND STATE-LEVEL SURFICIAL GEOLOGY (2) DEVELOP A SPATIALLY-CONTINUOUS NONERGODIC SITE TERM FOR GMMS IN UTAH USING GEOSPATIAL VARIABLES AND STATE-LEVEL SURFICIAL GEOLOGY AND (3) COMPARE THE RESULTS OF THESE MODELS WITH OTHER PUBLISHED ERGODIC AND NONERGODIC GMMS IN TERMS OF SITE-TO-SITE VARIABILITY REDUCTION, AND PROVIDE RECOMMENDATIONS ON ADDING SITE-SPECIFIC GEOTECHNICAL SITE CHARACTERIZATION FOR FURTHER UNCERTAINTY REDUCTION.DELIVERABLES AND EXPECTED OUTCOMES: THE DELIVERABLES OF THIS RESEARCH WILL BE: (A) A GEOSPATIAL AND GEOLOGIC SITE TERMS DATASET FOR CALIFORNIA AND UTAH (B) MAP-BASED GEOSPATIAL AND GEOLOGY-BASED SITE TERMS FOR USE WITH AN ERGODIC BASE GMM FOR BOTH CALIFORNIA AND UTAH, AND (C) AN IMPLEMENTATION MODEL FOR USING ALL THREE LEVELS OF SITE TERMS (GEOSPATIAL, GEOLOGIC, AND GEOTECHNICAL) WITH EXISTING GROUND MOTION MODELS. THE SITE TERMS WILL BE PROVIDED IN GEOGRAPHIC INFORMATION SYSTEM (GIS) RASTER FORMAT FOR EASY ACCESS THROUGH AN ONLINE REPOSITORY.INTENDED BENEFICIARY(IES): THIS PROJECT IS FOCUSED ON CALIFORNIA AND UTAH. THE DEVELOPMENT OF GROUND MOTION MODELS USING BROADLY-AVAILABLE GEOSPATIAL AND GEOLOGICAL DATA WILL REDUCE THE UNCERTAINTY IN SEISMIC HAZARD ESTIMATIONS FOR EACH STATE. THIS PROJECT WILL THEREFORE BENEFIT PUBLIC AGENCIES, STATE AGENCIES, FEDERAL AGENCIES, AND STAKEHOLDERS THAT PERFORM SEISMIC DESIGN IN THESE REGIONS. MOREOVER, THE GROUND-MOTION MODELING FRAMEWORK THAT WE DEVELOP COULD BE APPLIED TO BROADER AREAS IN THE FUTURE. THE LONG-TERM GOAL OF THIS RESEARCH IS TO IMPROVE THE SITE TERM MODELS FOR USE IN NONERGODIC GMMS, WHICH WILL PROVIDE HIGHER RESOLUTION AND MORE ACCURATE ESTIMATES OF GROUND MOTIONS FOR SEISMIC HAZARD ASSESSMENT AND USE IN REAL TIME GROUND MOTION PRODUCTS. IN ADDITION, THIS PROJECT WILL IMPACT THE PROFESSIONAL DEVELOPMENT OF ONE GRADUATE STUDENT RESEARCHER AND ONE UNDERGRADUATE STUDENT RESEARCHER, AS WELL AS STUDENTS AT BOTH TUFTS UNIVERSITY AND MERRIMACK COLLEGE.SUBRECIPIENT ACTIVITIES: N A