Origin of Selfhealing Pulses in Earthquake Dynamics

One of the most interesting results of kinematic and dynamic earthquake models is the pervasive presence of what Heaton called self-healing rupture pulses. Similar pulses have been found recently in the decollement of gels in contact with metal by Rubio and Baumberger and in the slip between dissimilar surfaces by serveral authors. Thus pulses seem to be a quite common feature of unstable slip under shear. We examine two possible models of healing: an active one where healing is the consequence of rate dependence of friction as proposed by Heaton and Cochard and Madariaga. Another is spontaneous healing due to heterogeneity of initial conditions proposed by Mikumo and Beroza. These two mechanisms are very different, in the former healing propagates at supershear speeds, while in the second subshear healing was found in some initial models of self-similar self-healing faults. We report on some general results about healing in shear faulting. Using Kostrov's 1994-1966 theory we demonstrate that healing fronts are propagating singularities of lower order than rupture fronts with no localised energy flow into or out of the fault. In many models healing is incomplete leaving small residual slip rates, on others healing can be total. We demonstrate that healing is a very effective method to reduce energy release during seismic rupture and unstable shear slip. Partial or total healing reduces the energy available for rupture to propagate, favoring ruture arrest and reducing seismic radiation.