Is pressure stimulated current relaxation in amphibolite a case of non-extensivity?
1 Technological Educational Institution of Crete - 73133, Chania, Greece, EU
2 UCL Institute for Risks and Disaster Reduction - London, UK, EU
3 Technological Educational Institution of Athens - 12210, Athens, Greece, EU
Received: 4 April 2012
Accepted: 15 June 2012
The application of uniaxial stress on rocks is accompanied by the production of an electric signal which is described by the term pressure stimulated current (PSC). In this work the high rate step stress (HRSS) technique is applied, and the PSC relaxation in amphibolite samples from KTB drilling, is studied in the frame of non-extensive statistical mechanics. After the application of an abrupt stress step, a PSC spike is recorded up to its maximum value PSCmax, decreasing gradually, right after the stress stabilization in a value σH. In the present work we study PSCs relaxation in uniaxial compressed rocks using a generalized exponential function called q-exponential, which explicitly introduces hierarchically constrained dynamics and interactions. The interactions are associated with the non-extensive entropy parameter q which exhibits a behavior indicating a dependence with the applied uniaxial stress as we approach fracture. The stress-dependent q-estimation leads to the conclusion that fracturing is a subextensive process with hierarchically constrained dynamics. Furthermore, assuming an assembly of relaxed subdomains created due to microfracture, a non-extensive behavior of the observed macroscopically PSC relaxation is discussed in the frame of a superstatistical approach.
PACS: 89.75.Da – Systems obeying scaling laws / 89.75.-k – Complex systems / 91.30.Px – Earthquakes
© EPLA, 2012