Inelastic behavior and failure of solids, especially geomaterials; coupling of deformation with pore fluid diffusion. Applications to deformation of the Earth`s crust, mechanics of earthquakes, hydrocarbon recovery and sequestration of carbon dioxide. More specifically, he is interested in the mechanics of earthquake faulting, the coupling of deformation and diffusion in the earth`s crust, and constitutive models for rocks, especially in relation to the analyses for the development of localized deformation.