The mechanics of seismic faulting: recent advances and open issues

In the early years '60 the fracture mechanics was mainly focused on tensile cracks (of prominent importance in engineering problems) and later on shear, antiplane cracks. Since these studies consisted in singular problems without friction, their applicability to earthquake events was extremely limited. After the seminal papers by Kostrov in the late years '60 and the relevant contributions of Aki, Burridge, Andrews, Das, Ida, Madariaga and others in years '70, more elaborated, realistic and physically constrained fault models have been proposed and further intensively used and improved. Complemented by the evidence from laboratory experiments on fracture (first pioneered by Ohnaka and later by Rosakis) and friction (pioneered by Dieterich, Ruina and more recently by Shimamoto), numerical and theoretical models provide substantial improvements in the understanding of the chemical and physical, potentially competing, energy-dissipating processes occurring in the natural fault structures. In spite of these significant advances, some open issues still hover and many important ideas remain unexplored fully. Relevant challenges to relate the physics of the seismic source to the coseismic scenarios and ultimately to the seismic hazard assessment could be successfully handled in the framework of a multidisciplinary approach, which combines theory, numerical models, data analysis, geological observations and laboratory experiments.