Abstract

"Slow Dynamics" Response of Geomaterial Moduli as a Function of Temperature

T.W.Darling, P.A.Johnson, J.A.TenCate, D.Pasqualini (Los Alamos National Laboratory, Los Alamos, NM, USA)

e-mail: darling@lanl.gov

"Slow Dynamics" is the term used to describe the observed logarithmic recovery of elastic properties of a material after a strain impulse. The impulse may be a thermal shock, an impulsive strike, or a short period of high amplitude oscillation. The recovery behaviour may be observed even when the impulse is well within the elastic limit of the material. There seems to be a connection between the variation of the low temperature elastic moduli and the degree of slow dynamical behaviour [T. J. Ulrich and T. W. Darling, Geophys. Res. Lett., v.28, pp. 2293-2296, 2001]. We will present Resonant Ultrasound Spectroscopy (RUS) data where we examine the response of the elastic moduli of several geomaterials to temperature impulses of a few degrees, as a function of temperature. The apparent bistable nature of the elastic moduli of Berea sandstone allows us, by measuring in each state, to test whether the slow dynamics are based in a strain induced transition between states, or in a thermally activated process active in every state.

Section : 3