Abstract:
The problem of seismicity physics reduces in a first approximation to the stability of a system of defects in a stress field. The characteristics of fractal properties of the lithosphere throughout its volume can be estimated from seismic wave scattering by studying the coda of local earthquakes and explosions. This analysis is based on digital recordings of local southern California earthquakes for 1992. Experimental determination of coda attenuation as a function of frequency gave fractal dimensions of the system of scattering defects along the paths concerned. Fractal dimensions were also found for a set of earthquake hypocenters using the catalog of the Southern California Earthquake Center for the period 1983-1996. The fact that the fractal dimensions of the seismicity were close to the sizes of the system of earth inhomogeneities corroborates the hypothesis that the long-term self-similarity of seismicity is controlled by earth structure, and shows the coda to be a promising tool for investigating the fractal properties of the lithosphere as applied to the physics of seismicity.