Strike-slip faulting on Titan: Modeling tidal stresses and shear failure conditions due to pore fluid interactions

Expressions of strike-slip faulting are well documented on multiple ocean worlds (e.g., Europa, Enceladus, and Ganymede) and the motion along these faults is thought to be driven by variations in diurnal tidal stresses. Titan exhibits a complex and dynamic geology with a varied surface morphology developed from fluvial, aeolian, and possible cryovolcanic and tectonic activity. However, observational data are currently limited and no clear strike-slip indicators have been identified so far. Nevertheless, the inferred presence of a porous ice layer saturated with liquid hydrocarbons in Titan's shallow subsurface provides a unique environment for studying zones of frictional weakness, shear heating, and the promotion of cryovolcanism. This study examines Titan's ability to host shear deformation mechanisms, including considerations for how the presence of near-surface liquid hydrocarbons and the crustal porosity of ice significantly reduce the resistance to shear failure of strike-slip faults in flexed areas under maximum diurnal tidal stresses. We conduct a sensitivity analysis of Titan's shear failure tendencies, given optimal failure conditions that may exist due to pore fluid interactions, and we examine the possibility for strike-slip tectonics guided by Coulomb failure laws and tidal stress mechanisms. Using the SatStress tidal stress model for a Titan-appropriate rheology, we compute the diurnal tidal stress tensor and resolve shear and normal stresses onto a suite of fault orientations. We adopt plausible coefficients of friction and include the effect of a hydrostatic pore fluid pressure gradient for Titan. At shallow fault depths (< 1 km) and for optimally oriented faults, this exploratory model suggests shear failure is achievable under diurnal tidal stress conditions subject to such pore fluid pressures, especially in the polar regions. Our results suggest that under these conditions, shear failure is not only possible, but may be an active deformation mechanism on the surface and in the subsurface of Titan, and could potentially serve as a pathway for the exchange of surface and subsurface materials through shear heating mechanisms. Moreover, the inference of conditions supporting strike-slip tectonism on Titan could have important implications for future Dragonfly observations and for future studies directed at better understanding the structural development of the surfaces of icy moons.