Earthquake physics beyond the linear fracture mechanics: A discrete approach

Abstract

Fast development of seismology and related disciplines like seismic prospecting observed in recent decades has its roots in efficient applications of ideas of continuum media mechanics to describe seismic wave propagation through the Earth. Using the same approach enhanced by fracture mechanics methods to describe physical processes leading to nucleation, development and finally arresting of earthquake ruptures has also advanced our understanding of earthquake physics. However, in this case, we can talk only about a partial success since many aspects of earthquake processes are still very poorly understood if at all. We argue that to progress with seismic source analysis we need to turn our attention to a complementary approach, namely a 'discrete' one. We demonstrate here that taking into account discreteness of solid materials we are able not only to incorporate classical 'continuum' solutions but also reveal many details of fracture processes whose analysis is beyond the classical fracture mechanics. In this paper, we analyse tensional processes encountered in rock mechanics laboratory experiments, mining seismology and sometimes in realistic inter-plate seismic episodes. The 'discreteness' principle is implemented through the discrete element method - the numerical method entirely based on the discrete representation of the medium. Special attention is paid to energy accumulation and transformation during loading and relaxation phases of fragmentation processes. This article is part of the theme issue 'Fracture dynamics of solid materials: from particles to the globe'.