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. Timonen1
1 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)
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