A new and very practical nonlinear least-square inversion method has been developed to investigate the dislocation distribution and the character of rupture propagation on an earthquake fault plane. The problem is parameterized using a model in which the fault is composed of subfaults which start rupturing with arbitrary magnitudes at arbitrary times.
The performance of the method is examined by numerical simulations, and the method proves useful for the analysis of source processes of earthquakes, including complicated cases such as multiple events. The source process of the Naganoken-Seibu earthquake of 1984 has been analyzed using strong motion seismograms. The dislocation distribution and the character of rupture propagation have been successfully obtained.