ROCK FLUID INTERACTION AND ITS EFFECT ON BRITTLE ROCK DEFORMATION

Abstract

Accurate assessments of Earth’s dynamic processes, which produce earthquakes and volcanoes, require better understanding of rock deformation. All rocks, to some extent, contain pores. In the Earth’s crust, the pore space is usually filled with water and other fluids such as CO2. Interactions between a rock and the interstitial fluids can significantly alter the physical and chemical properties of the rock and consequently how the rock deforms. My dissertation research focuses on how fluid-rock interactions affect brittle rock deformation including fracture growth and frictional slip that are central to earthquake mechanics, energy exploration and waste deposits.

I use both conventional experimental methods and the state-of-the-art synchrotron-based X-ray tomography to quantify the changes of mechanical properties and 3-dimensional pore structures of deforming rocks. The two major findings are: 1) olivine carbonation reactions, in which carbon dioxide is chemically incorporated into silicates to form carbonate, can produce nano- to micro-scale dissolution channels as well as expansion cracks in the host rocks, suggesting that olivine carbonation can be self-sustaining despite its large positive volume change. By identifying the mechanisms that generate porosity during olivine carbonation, this work provides new insights into the application of CO2 mineral sequestration; 2) increasing pore pressure impedes fracture propagation in intact rocks and stabilizes slip along gouge-bearing faults. The stabilizing effect is positively correlated with pore volume increases, suggesting that dilatant hardening is responsible for the observed strengthening. These results provide new physical understanding of the observed spatial correlation between slow slip events and high pore pressure in many subduction zones where tsunami-generating mega earthquakes occur.