The four-dimensional evolution of normal faults

Abstract

Normal faults play a crucial role in understanding the dynamic processes of the Earth, shaping landscapes, influencing sedimentary basins’ distribution, energy resources, and impacting seismic activities. However, much remains to be unravelled, such as the variation of slip rates over time and changes in a fault’s sealing potential throughout its lifespan. In this thesis, I investigate the geometric and kinematic variability of normal faults over time and their implications for fluid flow using age-constrained 3D seismic reflection and wellbore data from the SW Barents Sea. First, I constrain the four-dimensional evolution of extensional growth folds using the stratigraphic record. This reveals that fault-propagation folding can occur in multiple phases, as a protracted process. Next, I focus on the understudied early stage of normal fault growth, providing critical observational datasets that contribute to fault growth models. The results show that there is no universal law that explains normal fault growth. Instead, variability is observed even within faults in the same basin. Local differences in fault initiation times and strain distribution not only affect the final dimensions of faults but also impact the fault length to height aspect ratios. Faults in the early stages of development grow following the constantlength model, reaching near-final lengths before accumulating significant displacement and thus exhibiting geometric immaturity. I investigate the influence of fault geometry and kinematics on fault seal potential. and explore the capabilities of FWI models in determining the P-wave velocity of fault zones. My research indicates an influence of fault growth patterns on fault seal potential. My work demonstrates that fault zones often exhibit variability in their P-wave velocity structure, reflecting the natural heterogeneity observed in faults studied in outcrops. This contributes towards improving our understanding of the physical properties of fault zones by combining seismic reflection and FWI velocity data.