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Extended abstract for the 11th International Conference on Fracture 2005 1 EFFECTS OF NON-LINEAR WEAKENING ON

Summary: Extended abstract for the 11th International Conference on Fracture 2005 1
J.-P. Ampuero
Geosciences Department, Princeton University, USA
An earthquake is usually modeled as an extension of the Dugdale approach: as in LEFM, fracture energy Gc
is completely spent in a relatively small region close to the crack tip, the process zone; and the fault strength
is described by a slip weakening law that reaches a residual level at a characteristic slip Dc. Beyond its
regularizing properties, slip weakening is a phenomenological fact of experimental rock mechanics. Recent
laboratory observations show that slip weakening can be a persistent process over large amounts of slip, in
contradiction to our usual view of a finite Dc. New seismological constraints from seismic nucleation phases
and from the scaling of radiated energy with magnitude, seem to point to a similar interpretation. Persistent
weakening can also be viewed as a lumped representation of off-fault non linear processes occurring in the
wake of the process zone. On this basis, power law weakening laws have been proposed that feature a very
steep weakening rate in the short slip range followed by a long tailed, non linear, weakening process with
no characteristic slip. On the other hand there is growing interest in the apparent scaling of fault properties,
such as Dc and Gc, with earthquake size. This is a key issue in understanding how much can be learned
about large destructive earthquakes from the observation of smaller but more frequent ones and from laboratory
experiments. I explore here the possible effects of non linear strength drop on macroscopic earthquake source


Source: Ampuero, Jean Paul - Division of Geological and Planetary Sciences, California Institute of Technology


Collections: Geosciences