Consistent Framework for PGA Estimation at Liquefaction Case History Sites: Application to the 1989 M6.9 Loma Prieta Earthquake

Evaluations of liquefaction triggering and effects are commonly assessed by representing demand with intensity measures (IMs) such as peak ground acceleration (PGA), supplemented with earthquake magnitude (M). Past approaches estimated IMs at liquefaction case history sites by taking the recorded value from a nearby seismic station, estimating the IM using ground motion models or 1D site response analyses, and/or based on judgment. These approaches might not account for one or both of the following: (1) the differences in path and site effects between the site of interest and the nearest recording; and (2) the IM spatial correlation structure. A framework that addresses these limitations is presented and used to estimate PGA values at case history sites of the 1989 Loma Prieta Earthquake as a case example. Findings from this study suggest that PGAs computed using the presented framework differ from those traditionally used in the development of liquefaction triggering models.