9416546 Beroza This research is to model strong-motion data of the Northridge earthquake in order to estimate the factors controlling earthquake rupture and to understand the component of the strong ground motion attributable to the earthquake source. A unique aspect of the near-source data for this earthquake is that a number of high dynamic range digital accelerographs recorded the initiation. Like the Loma Prieta and Landers earthquakes before it, the Northridge earthquake began gradually before breaking out into a large event. A goal is to understand how earthquakes nucleate. Preliminary work on this event and many other earthquakes indicates that there may be a distinct nucleation phase at the beginning of most earthquakes. This project is a contribution to the National Earthquake Hazard Reduction Program and is supported by the Northridge Earthquake Emergency Appropriation. ***
