Abstract
The electrical behaviour of marble samples from Penteli Mountain was studied while they were subjected to uni- axial stress. The application of consecutive impulsive variations of uniaxial stress to thirty connatural samples produced Pressure Stimulated Currents (PSC). The linear relationship between the recorded PSC and the applied variation rate was investigated. The main results are the following: as far as the samples were under pressure cor- responding to their elastic region, the maximum PSC value obeyed a linear law with respect to pressure varia- tion. In the plastic region deviations were observed which were due to variations of Young's modulus. Further- more, a special burst form of PSC recordings during failure is presented. The latter is emitted when irregular lon- gitudinal splitting is observed during failure.
Highlights
Transient electric phenomena in the lithosphere have been observed for a long time (Varotsos and Alexopoulos, 1984a,b; Fujinawa and Takahashi, 1990; Nomicos and Vallianatos, 1997; Hayakawa, 1999)
In a set of previously conducted Pressure Stimulated Currents (PSC) experiments on marble samples (Stavrakas et al, 2003; Vallianatos et al, 2004), the samples were subjected to uniaxial stress in the elastic range of the material
We first established a correlation between the emitted PSC and the applied stress rate
Summary
Transient electric phenomena in the lithosphere have been observed for a long time (Varotsos and Alexopoulos, 1984a,b; Fujinawa and Takahashi, 1990; Nomicos and Vallianatos, 1997; Hayakawa, 1999). Since electric phenomena are observed during fracturing of dried rocks it is evident that both piezoelectric and electrokinetic effects may not be the main factors for modeling such phenomena. Since transient electric phenomena are promising candidates as earthquake precursors, a series of laboratory experiments of uniaxial compression of marble samples were carried out to understand the underlying physical mechanisms of electric signal generation. We show experimental results obtained in the case of applying stress that produced deformations in the plastic range up to fracture. The results suggest that the proportionality factor γ between the emitted current (I) and the stress rate (dS/dt) changes as we pass to the plastic region, in consistency with the MCD model. An experimental attempt to understand an electrical activity (i.e a series of short pulses) observed approaching failure is given
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
