The hydromechanical properties of the uppermost basement and of the basement–sediment interface influence multiple geologic processes of societal relevance, including the flow of groundwater; the accumulation of hydrocarbons, economic minerals, and geothermal resources; and the response of seismogenic faults to wastewater disposal. Lithologic, structural, and metamorphic fabric; uplift; weathering and alteration history; and the nature of the overlying strata all play roles in controlling these hydromechanical properties.