Chapter 10 Shear band thermodynamic model of fracturing

Abstract

This chapter presents a new model of the seismic source zone based on the thermodynamics of line defects. Dislocational superlattice plays an essential role in the thermodynamics of line defects. The line vacancies enable to construct a superlattice consisting of dislocations and vacant dislocations. The depth distribution of the superlattice constant Λ in the Earth's mantle may follow from the consistency condition between the dislocation and thermodynamic models of the seismic source. The model fits the plastic deformations. Because of stress load, some changes of dislocation density may be expected related to the superlattice model. Such changes can be related to a change in the number of vacant dislocations or to a change in the superlattice parameter Λ. As assumed in the model, the plastic deformations are realized by the formation of shear bands. A dislocation number increases intensively along the shear planes and exceeds the number prescribed by the Λ structure of the superlattice. The shear band thermodynamic model is combined with the method of estimating the top stress values before fracturing for sequences of events in a confined seismic region. When considering the dislocation superlattice, the influence of some distortions on the dislocation lines —namely, kinks and jogs are also included.