Fault zones are complex and highly variable systems that can govern crustal fluid flow at a range of scales (microscale to macroscale, across-fault flow and up-fault flow, and from depth towards surface). However, predicting the hydraulic and mechanical properties of fault zones remains difficult. This has implications for a range of geological engineering applications, including geoenergy activities such as carbon capture and storage, or geothermal heat, where determining the influence of faults on flow is critical to evaluate site performance and to guide site selection. Further, to date, much of previous work on fluid flow processes in fault zones have concentrated on the deep subsurface (for oil and gas applications). Thus, very little is currently known on how fault characteristics are altered by near-surface effects towards the surface, which is relevant for predicting, monitoring, and remediating any potential impacts from leakage to surface from geoenergy engineering activities.