11:30 AM - 11:45 AM
[J06-4-05] The dynamic stiffness as the indicator of slip mode and transition of the fault to a metastable stage.
Studied is the gradual transition from unstable to stable frictional sliding in laboratory experiment. The behavior of gouge-filled fault was investigated at the experimental setup based on the spring-bock slider model. We document transitions between different modes of sliding as the result of changing proportion of gouge components. The values of scaled kinetic energy typical for events inherent to those modes differ by several orders of magnitude, while differences in contact strengths and amplitudes of shear stress drops remain relatively small. The parameter of the fault, which is very sensitive to changes of gouge composition is the maximal rate of frictional resistance weakening ks. The obtained results allow concluding that the slip mode is controlled by the ratio of ks to the stiffness of enclosing rock massif.
The value of ks is closely coupled with the fault specific shear dynamic stiffness. The latter can be determined from measurements of the parameters of seismic waves passing through or reflected from a fault. The technique of stiffness estimation was developed in our previous studies and tested in laboratory and 'in situ' observations.
We document that the dynamic stiffness of model fault drop drastically before both stick-slip events and slow slip events. The Shear stiffness decrease begins long before the macroscopic displacement is recorded. In our experiments, the time of precursor manifestation was up to 1/3 of the duration of the “seismic cycle."
If similar mechanisms operate in nature, the effect of fault evolution to a metastable stage can be revealed through active and/or passive seismic monitoring of fault zones. This effect manifests both in the parameters of seismic waves reflected from the fault, and in the spectra of microseismic noise, which had already been registered before several powerful earthquakes.
The value of ks is closely coupled with the fault specific shear dynamic stiffness. The latter can be determined from measurements of the parameters of seismic waves passing through or reflected from a fault. The technique of stiffness estimation was developed in our previous studies and tested in laboratory and 'in situ' observations.
We document that the dynamic stiffness of model fault drop drastically before both stick-slip events and slow slip events. The Shear stiffness decrease begins long before the macroscopic displacement is recorded. In our experiments, the time of precursor manifestation was up to 1/3 of the duration of the “seismic cycle."
If similar mechanisms operate in nature, the effect of fault evolution to a metastable stage can be revealed through active and/or passive seismic monitoring of fault zones. This effect manifests both in the parameters of seismic waves reflected from the fault, and in the spectra of microseismic noise, which had already been registered before several powerful earthquakes.