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Geophysical Research Abstracts, Vol. 5, 11288, 2003 c European Geophysical Society 2003
 

Summary: Geophysical Research Abstracts, Vol. 5, 11288, 2003
c European Geophysical Society 2003
EFFECTIVE FAULT FRICTION AND SEISMIC
NUCLEATION PHASE: SCALE-DEPENDENT OR
NON-LINEAR FRICTION ?
J.P. Ampuero (1) and J.P. Vilotte (2)
(1) Department of Geosciences, Princeton University (jampuero@princeton.edu), (2)
Département de Sismologie, Institut de Physique du Globe de Paris (vilotte@ipgp.jussieu.fr)
We show how fault friction properties can be retrieved from the shape of the gradual
onset of some seismograms. Based on a mechanical model, we derive a method to
estimate the slip weakening rate W from an exponential fit to the seismic nucleation
phase. Clues on fault zone structure and state of stress can be additionnaly obtained
in the same process. The basic ingredients of the model are: (1) linear slip weak-
ening friction on a planar fault, (2) a non uniform, locally peaked, prestress and (3) a
slow tectonic load at constant rate. As characterized by numerical and analytical tools,
the nucleation process is composed of two phases: (I) quasi-static nucleation and (II)
dynamic nucleation. Phase I starts as soon as the stress overcomes fault strength in
the region of initial stress concentration. It is characterized by stable slip on a slowly
growing patch, driven by the slow tectonic load, and ends when the size of the slipping
patch reaches the critical size Lc µ/2W. Phase II is dynamically unstable and is

  

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

 

Collections: Geosciences