Eur. Phys. J. E 4, 273-279
Fragmentation dynamics within shear bands-a model for aging tectonic faults?
J.A. Åström1, H.J. Herrmann2 and J. Timonen11 Department of Physics, University of Jyväskylä, P.O. box 35, FIN-40351 Jyväskylä, Finland
2 University of Stuttgart, Pfaffenwaldring 27, D-70569 Stuttgart, Germany
(Received 26 July 2000)
Abstract
A numerical model for packing of fragmenting
blocks in a shear band is introduced, and its dynamics is
compared with that of a tectonic fault.
The shear band undergoes a slow aging process in which
the blocks are being grinded by the shear motion and
the compression.
The dynamics of the model have the same
statistical characteristics as the seismic activity in
faults. The characteristic magnitude distribution
of earthquakes appears to result from frictional slips at
small and medium magnitudes, and from fragmentation of blocks at the
largest magnitudes. Aftershocks to large-magnitude earthquakes
are local recombinations of the fragments before
they reach a new quasi-static equilibrium. The aftershocks
satisfy Omori's law. Local precursor activity at a few times the
normal background level appears at a short time
before a major earthquake. Seismic gaps appear
as a natural consequence of the aging process of a fault.
Explanation of the heat flux and principal stress direction
anomalies at the faults both involve the value of fracture stress
of the blocks in the gouge.
The final form of a tectonic fault is predicted to involve
a gouge dominated by fine-grained and rather rounded blocks
so that it cannot withstand large shear stresses.
91.45.Vz - Fractures and faults.
45.70.-n - Granular systems.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001
