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Fracture and Faulting |
CSIRO Division of Geomechanics, PO Box 54, Mt Waverley, Vic 3149 Australia
Velocity-stepping sliding experiments on a 0.1 m2 interface between two gabbro blocks under 0.5–2.0 MPa normal stress have shown consistent velocity-weakening behaviour. The parameter values are in a similar range to those measured on other materials in other laboratories. However, simulation of the complete transient behaviour requires a second state-variable which has a characteristic decay distance c. 100 x longer than the first, and with the opposite sign (velocity-strengthening). The second delayed effect is not sufficient to cancel out the short period effect, and is not expected to control the onset of unstable stick-slip sliding. These experiments extend the observed realm of velocity-weakening behaviour to larger interfaces and lower normal stresses than has been previously reported.
