Slow motions as inelastic strain autowaves in ductile and brittle media

Abstract

Here we provide a review of research on slow motions and strain waves in the Earth and propose a substantiated hypothesis that all stress-strain perturbations in the form of slow waves propagating in solids and geomedia, including plastic waves in metals and waves in faults of different scales, are of common physical nature. Loaded solids and geomedia are active hierarchically organized multiscale systems that display nonlinear dynamics and lose their stability when disturbed by any dynamic processes at block boundaries, e.g., displacements in fault zones. Such a medium cooperatively responds to parametric excitation by generating slow strain waves (autowaves) as a way of its self-organization. In support of the proposed concept, a consistent mathematical model is suggested for describing the evolution of stress-strain states and slow strain autowaves in an unstable elastoplastic medium, and examples of simulations are presented for strain autowaves in ductile materials under tension and quasi-brittle materials and geomedia with a fault zone under compression.