Rupture propagation, dynamical front selection, and the role of small length scales in a model of an earthquake fault

We examine a model of rupture propagation on a one-dimensional earthquake fault, focusing both on the role of small length scales in controlling the dynamics and on the mechanisms by which propagating modes are selected. In order to obtain a well-defined continuum theory, we add a small amount of viscous dissipation to a previously studied model in which rupture propagation was controlled by a finite-difference grid spacing. We find that the dynamically selected rupture mode is one in which nearly free slip occurs in a pulse whose speed and shape are determined by a novel selection mechanism.