<p>The displacement and strain distributions caused by fault slip fundamentally determine the characteristics and extent of the deformation and failure of tunnel structures. In this paper, granite planar fault samples and granite asperity fault samples were prepared. From the perspective of the influence on the tunnel, direct shear tests and digital image correlation (DIC) technology were used to study the evolution of the horizontal displacement and shear strain caused by fault slip and the influence of roughness. The experimental results illustrate that fault slip can be divided into three stages, namely, the stick stage, the chaotic stick–slip stage, and the stick–slip stage. The shear contraction mainly occurs when the fault dislocation occurs, and the rougher the fault plane is, the greater the degree of shear contraction is. The evolution of the horizontal displacement is a process in which the uneven distribution of the horizontal displacement is gradually localized, and the fault slip eventually tends to become centralized. The evolution of the shear strain is a process in which the shear strain is localized and an influence band of shear strain forms. The larger the roughness is, the easier it is for cracks to initiate. The propagation of cracks leads to uneven distributions of horizontal displacement and shear strain on both sides of the crack. The research achievement expands the understanding of mechanical response characteristics of fault under the action of fault slip, and the results can be used as a design basis for underground projects across active faults.</p>