How the Earth’s upper crust deforms in a viscous or brittle manner and how these behaviors interact and evolve over time: the crucial role of pressure solution creep and sealing processes1

Abstract

Observations of the geological deformation of the Earth’s upper crust show both brittle behavior (faults) and viscous behavior (folds, shear zones). This paper explains the crucial role of pressure solution creep and sealing processes in these contrasting behaviors and in their evolutions over time. A description of natural deformation by pressure solution shows that the pressure solution creep process can accommodate large ductile deformation without any faults. This process can also accommodate near-stable ductile deformation through the coupling of pressure solution and fracturing. Even if pressure solution creep cannot accommodate the tectonic loading rate and earthquakes consequently occur, the post-seismic evolution is largely controlled by pressure solution processes such as post-seismic creep and fault healing and sealing. Some key experiments are presented that allow evaluating the thermodynamics and kinetics of these processes. Various models are then presented that could help engineers integrate pressure solution creep and sealing processes into predictions of the long-term behavior of rock deformation in underground storage and geo-energy facilities.