Mechanical and geological controls on the long-term evolution of normal faults

Abstract

This thesis investigates the long-term evolution of rift-bounding normal faults in extensional environments. My main objective is to develop a theoretical framework that explains the controls on maximum fault offset in terms of a few key mechanical and geological controls. In Chapter 2, I propose that flexural rotation of the active fault plane enables faults to evolve along a path of minimal energy, thereby enhancing their life span. In Chapter 3, I show that surface processes can increase the life span of continental faults by reducing the energy cost of topography build-up. In Chapter 4, I focus on lithospheric bending induced by fault growth. I demonstrate that numerical models that treat the lithosphere as a visco-plastic solid properly predict fault evolution only when the rate-dependent viscous flexural wavelength of the lithosphere is accommodated within the numerical domain. In Chapter 5, I investigate the growth of normal faults in relation to a depth-variable rate of magma emplacement. These models predict both faulting styles and crustal architecture at slow mid-ocean ridges. Finally, in Chapter 6 I use a newly developed 3-D numerical model to establish a relation between along-axis fault continuity and spatial heterogeneities in lithospheric thickness at a ridge segment.