14 Earthquakes as a complex system

Abstract

Earthquakes are a direct consequence of the deformation of the Earth's crust. They are primarily associated with stick-slip behavior on preexisting faults. This chapter focuses on an approach to earthquake mechanics in which the crust is considered as a complex self-organizing system that can be treated by techniques developed in statistical physics. The basic hypothesis states that deformation processes interact on a range of scales from thousands of kilometers to millimeters or less. The chapter explores the validity of Gutenberg–Richter frequency–magnitude relation for both regional and global earthquakes. It examines the idea that complex phenomena often exhibit fractal scaling in magnitude, space, and time. Complex phenomena also exhibit chaotic behavior. Concepts of complexity also have direct applicability to probabilistic earthquake hazard studies and to intermediate-term earthquake prediction. The universal applicability of the Gutenberg–Richter relation provides one of the principal means of estimating the earthquake hazards. The rate of occurrence of small earthquakes provides a quantitative measure of the rate of occurrence of larger earthquakes. The concepts of complexity thus provide a rational basis for extrapolation and for intermediate-range earthquake prediction.