Brittle Deformation of Solid and Granular Materials with Applications to Mechanics of Earthquakes and Faults

Abstract

Crustal fault zones are complex regions of localized deformation with fractured, cataclastic and pulverized rocks having evolving geometries and altered rheological properties from those of the host material. At some level of fracture density (damage) the cohesive matrix of the material is destroyed and the associated volume becomes granular. The occurrence of seismic ruptures, and healing phases in the interseismic periods, continually modify the damage and granularity. This produces evolution of the elasticity, permeability and geometry of the actively deforming regions. The evolution of fault zone structures leads, in turn, to changes in the properties of dynamic earthquake ruptures, seismic radiation, inter- and post-seismic deformation, and local seismicity patterns. Many fundamental aspects of brittle deformation in crustal rocks remain unsolved. Basic examples include: What are the proper metrics to characterize brittle rock damage and the transitions between damaged rock and granular material? What are the main similarities and differences between the dynamics of damaged rocks and granular media? What are the characteristics of nonlinear stress–strain behavior of damaged rocks and how can they be modeled quantitatively? How much slip is localized on main rupture surfaces and how much is distributed in the bulk for various fault environments? The 16 papers in this volume provide recent theoretical and observational perspectives that address the above and related issues. Topics include damage rheology models, high-resolution measurements of nonlinear evolving elasticity, high-resolution experiments on frictional instabilities and dynamic ruptures, theoretical and observational results on different dynamic regimes of sheared solids and granular materials, effects of fluids and roughness on fault zone rheology, seismic radiation near fault kinks, and geological and laboratory characterizations of fault surfaces and damaged rocks.