Before revision: He is best known for his 1968 seminal paper " Engineering Seismic Risk Analysis " that started the field of Probabilistic Seismic Hazard analysis (PSHA), his work in reliability especially on second-moment methods and reliability-based code calibration, and his development of the probabilistic framework for performance-based earthquake engineering that became the unifying equation of the Pacific Earthquake Engineering Research (PEER) Center.
After revision: He is best known for his 1968 seminal paper Engineering Seismic Risk Analysis that started the field of Probabilistic Seismic Hazard analysis (PSHA), his work in reliability especially on second-moment methods and reliability-based code calibration, and his development of the probabilistic framework for performance-based earthquake engineering that became the unifying equation of the Pacific Earthquake Engineering Research (PEER) Center.