Dielectric properties of Granodiorite partially saturated with water and   its correlation to the detection of seismic electric signals
  Transient electric signals emitted prior to earthquake occurrence are recorded at certain sites in the Earth's crust termed sensitive. These field observations enforce the laboratory investigation of the dielectric response of rocks forming these localities. The dielectric relaxation of granodiorite rock coming from such a sensitive locality (Keratea, Greece) reveals, through complex impedance spectroscopy, that the activation volume for relaxation of this rock is negative which so far has been reported only rarely. This result, however, supports a theoretical model on the pre-seismic electric signals and is likely to be correlated with the sensitivity of the site and hence with the selectivity. 
A.N. Papathanassiou, I. Sakellis, and J. Grammatikakis
physics.geo-ph