The orthogonal pattern of NE and NW striking wrinkle ridges in Hesperia Planum makes this area unique and enigmatic. The wrinkle ridge morphologies revealed in Mars Orbiter Laser Altimeter topography across ridge structures in Hesperia Planum suggest that wrinkle ridges form above thrust faults. The timing relationship among wrinkle ridge sets is evident in the digital elevation models; thrust faults striking NE are older than the NW striking ridges. The NE striking wrinkle ridges show unequal development adjacent to the NW striking wrinkle ridges, and an echelon pattern throughout Hesperia Planum; therefore formation by two independent sequential sets is not likely. Reactivation of the older (NE) thrust faults from the younger (NW) wrinkle ridges, inferred from the observations, is tested by resolving Coulomb failure stress changes along the older thrust faults from slip along the younger thrust faults. We find fault reactivation is likely in Hesperia Planum, regardless of the deposit material (basalt or tuff). Previously, the NE striking wrinkle ridges were interpreted as forming prior to, or contemporaneous to, the Tyrrhena Patera flank flow unit. This observation and the continuation of many of these ridges into the Noachian highlands as thrust fault scarps suggest formation of NE striking thrust faults no later than the late Noachian/early Hesperian. The NW striking wrinkle ridges, forming after the emplacement of the late Hesperian/early Amazonian Tyrrhena Patera deposit, imply geologically recent thrust faulting. The combination of NE and NW structural events implies a stress state rotation in Hesperia Planum of about 90¿ between the late Noachian and early Amazonian.