Time-dependent deformation of thermally-fractured granites observed in laboratory creep experiments.

Hiroki Sone, Mayukh Talukdar, & Katherine Condon

Published August 16, 2021, SCEC Contribution #11503, 2021 SCEC Annual Meeting Poster #120

Discrepancies between fault slip rates inferred from geological indicators and those inverted from geodetic velocities and kinematic block models have suggested that a significant fraction of relative plate motions are accommodated by off-fault deformation. It is important to understand where such off-fault deformation occurs (hidden fault vs. distributed rock deformation), and their rheology, as it influences the kinematics of plate motions and how stress accumulates in the crust and are released through seismic and aseismic deformation. Through laboratory rock mechanics experiments, we attempt to investigate the magnitude and constitutive relation of any time-dependent (or viscous) distributed deformation that may occur in damaged crustal rocks at relatively shallow depth conditions. Granite samples were heated to induce internal microfractures to represent analogue fault damage zone rocks. By applying isotropic and triaxial stresses in steps, and holding for an extended period of time between steps, we observe the creep behavior of the samples. Preliminary results confirm that the presence of microfractures enhance the time-dependent creep deformation of damaged rocks even at room temperature and in the absence of water. We further investigate whether the presence of pore water and moderate temperatures (90-200 degrees Celsius) enhance this behavior or not, potentially be mechanisms such as sub-critical crack growth and pressure solution. Results will provide quantitative data needed to evaluate the degree to which off-fault deformation could accommodate plate motion and also relax differential stresses during the interseismic period.

Citation
Sone, H., Talukdar, M., & Condon, K. (2021, 08). Time-dependent deformation of thermally-fractured granites observed in laboratory creep experiments.. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Stress and Deformation Over Time (SDOT)