Complex Earthquake Sequences On Simple Faults

While power law distributions in seismic moment and interevent times are ubiquitous in regional earthquake catalogs, the statistics of individual faults remains controversial. Continuum fault models without heterogeneity typically produce characteristic earthquakes or a narrow range of sizes, leading to the view that regional statistics originate from interaction of multiple faults. I present theoretical arguments and numerical simulations demonstrating that seismicity on homogeneous planar faults can span several orders of magnitude in rupture dimensions and interevent times, if the fault dimension W is sufficiently large compared to a characteristic length knit, related to the nucleation dimension. Large faults are increasingly less characteristic, with the fraction of system-size ruptures proportional to (L-erit/W)(1/2). Earthquake statistics for large W/L-erit is remarkably close to nature, exhibiting Omori decay and power law distributed rupture lengths. Simple crack models are consistent with a Gutenberg-Richter distribution with b = 3/4 and provide a physical basis for these distributions on individual faults.