Tara Nye, USGS Models of earthquake ground motion (both simulations and ground-motion models) can be likened to a puzzle with three primary pieces representing the earthquake source, site conditions, and source-to-site path. Early versions of these models were developed using average behavior of earthquakes across a variety of regions and tectonic environments. Although informative, such models do not capture the unique source, path, and site effects that are expected to have a significant influence on resulting ground motion. This talk highlights several approaches for improving modeling of ground motion by focusing efforts on the different pieces of the ground-motion puzzle. Segments of the talk include (1) constraining rupture parameters of rare tsunami earthquakes, (2) estimating site-specific high-frequency attenuation in the San Francisco Bay Area, and (3) investigating relationships between path effects and crustal properties in the San Francisco Bay Area. With continued refinement to models of ground motion, we can improve confidence and reduce uncertainty in seismic hazard and risk assessments.