9416120 Kanamori This research is to investigate the relationship between the 3-D crustal structure, the fault geometry and the dynamic characteristics of the Northridge earthquake sequence. The 1994 Northridge earthquake occurred on a south-dipping fault beneath the Transverse Ranges, in striking contrast to the 1971 San Fernando earthquake which occurred on a north-dipping fault. This will investigate why the two faults are segmented like this (north vs. south), and what prevented the rupture of the Northridge earthquake from extending further to the west. Since the Transverse Ranges involve many active structures formed under a regional north-south compressional stress system, a much larger earthquake than the Northridge earthquake could occur if the system, a much larger earthquake than the Northridge earthquake could occur if the rupture extended over many segments of faults. The work will also involve investigation of the variation of dynamic characteristics (waveform, stress drop, energy-moment ratio) of the major aftershocks in relation to the 3-D structure. This project is a contribution to the National Earthquake Hazard Reduction Program and is supported by the Northridge Earthquake Emergency Appropriation. ***
