9416342 Zhang This research is to determine source parameters of the Northridge earthquake that can be best resolved with broadband and long-period regional and teleseismic recordings. Parameters include total seismic moment, total rupture duration and the overall source geometry. Techniques to be used include complete waveform inversion of body wave and surface wave signals using an aspherical earth model with a centroid-moment tensor inversion approach; spectral inversion of fundamental mode surface waves with propagation corrections for an aspherical model; body and surface wave deconvolutions using empirical and theoretical Green's functions; and a combined broadband body waveform/surface wave spectra inversion for extracting a very broadband source model. The analysis will provide characterization of the long-period far- field source radiation, yielding basic constraints on the energy release, duration, and geometry of the faulting, which must be satisfied by more detailed models striving to match observed near- field motion. This project is a contribution to the National Earthquake Hazard Reduction Program and is supported by the Northridge Earthquake Emergency Appropriation. ***
