Earthquake scaling, the dependence of seismic source parameters on earthquake size, continues to be an area of active research. Advances in seismic instrumentation have lead to advances in our understanding of how earthquake parameters scale. A continuing debate centers on whether or not earthquakes undergo a breakdown in self-similarity at about the magnitude 3 level indicating a minimum source size of approximately 100 m [ Aki, 1987]. Abercrombie and Leary [1993] used recordings from the Cajon Pass well at a depth of about 2.5 km and found that stress drop of earthquakes in the magnitude 2 to 3 range did not show a breakdown in self-similarity They found that these earthquakes had stress drops comparable to larger events and source dimensions as small as 10 m. The minimum source size inferred in other studies, may instead be an artifact of an apparent corner frequency caused by not accounting for highly attenuating layers near the free surface.
Pacheco et al.J[1992]Jcompiled evidence that there is a breakdown in the frequency-magnitude relation at large magnitudes when the source size reaches the width of the seismogenic zone. This observation should have an impact on the use of the rate of small earthquakes to infer the rate of larger earthquakes. Studies by Romanowicz [1992], Romanowicz and Rundle [1993], and Scholz [1994] addressed the issue of the scaling of slip with earthquake size for very large earthquakes.