Fractal clustering of fault activity in California

We have studied the temporal distribution of paleoseismic records of earthquakes in several regions of California, over time scales ranging from decades to several hundreds of thousands years, by using dates obtained by electron spin resonance plateau dating of fault gouge, 14C dated sediments from fault zones, and records of historic earthquakes. The historical record in the San Andreas fault zone of central California and the paleoseismic record of the San Gabriel fault zone both exhibit self-similarity with a fractal dimension of 0.43–0.46. The fractal dimension of the San Andreas fault zone in southern California both in historic and paleoseismic time scales is 0.67, indicating more evenly distributed fault movements than those of central California. On time scales <1 yr, the distribution is largely random.