[S-CG50] Rheology, fracture and friction in Earth and planetary sciences

[SCG50-04] Simultaneous measurement of seismic velocity and electrical resistivity of mafic and ultramafic rocks during triaxial deformation under fluid-saturated condition

*Eranga Gayanath Jayawickrama¹, Ikuo Katayama¹ (1.Hiroshima University)

Keywords:Velocity, Resistivity, Crack

Various experimental investigations have shown that cracks embedded in rocks generate a significant effect on rocks’ physical properties such as static rock moduli, elastic wave velocity, and resistivity, under both hydrostatic and differential stress conditions. However, so far, experiments designed to investigate the effect of cracks on the above properties have only been capable of investigating those properties individually or two at most in combination, at a time. While the results of such experiments enlighten the geophysical observations to a certain degree, we find that it is of utmost necessity to investigate the crack effect on the above stated properties simultaneously, since cracks affect individual physical properties differently. Therefore, using a new 16-channel feedthrough system, we performed triaxial deformation experiments at Hiroshima University on thermally cracked mafic (diabase) and ultramafic (harzburgite) rocks under fully saturated conditions while simultaneously recording the porosity evolution, stress-strain response, elastic wave velocity, and resistivity. The results indicated a remarkable agreement among the various physical properties as the crack properties, such as crack density and aspect ratio, evolved with the increasing differential stress until catastrophic failure is occurred. In addition to these results, we further discuss the strength contrast of the thermally treated diabase and harzburgite that is in analogy to the damaged layered oceanic lithosphere.