Brittle Tectonics: A Non-linear Dynamical System

Abstract

Definition of the SubjectBrittle deformation is the primary mode of deformation of the Earth’s crust. At the long timescale it is manifested by faulting and on the short timescale by earthquakes. It is one of the best-known examples of a system exhibiting self-organized criticality. A full understanding of this system is essential to the evaluation of earthquake hazard. IntroductionThe upper part of the Earth’s crust is brittle and under a state of all-round compression. It responds to deformation by faulting: the formation and propagation of shear cracks. The crack walls support normal stresses, and hence fault propagation must overcome not only the rupture resistance of the fault tips but friction between its interior interfaces. This friction is usually velocity weakening, such that any slippage results in stick–slip instability. The resulting dynamically running crack-like shear instability radiates elastic waves, producing the shaking known as an earthquake. Thus brittle tectonics ...