STRIKE-SLIP TECTONISM ON GANYMEDE: INVESTIGATING COULOMB FAILURE AT A GLOBAL SCALE (Invited Presentation)

High-resolution Galileo solid-state imager data of Ganymede’s complex surface provides strong evidence that strike-slip tectonism, inferred previously from combinations of strike-slip indicators in nine regions, is important to the structural development of Ganymede’s surface. Moreover, tidal stresses may be sufficient to induce shear failure and generate strike-slip faulting. This study examines the stress magnitudes, fault depths, ice friction, and rheology that support shear failure of strike-slip fault zones on Ganymede. We use the numerical model SatStress to calculate both diurnal and non-synchronous rotation (NSR) tidal stresses at the surface. We resolve normal and shear stresses onto discrete fault segments of specified orientation and assess Coulomb failure stress for the nine inferred fault zones. Testing a range in ice friction, we find that models combining diurnal and NSR stress contributions readily generate shear and normal stress magnitudes that promote shear failure within each studied fault zone. High friction (μ_f = 0.6) limits failure depths to ~1 km, while low friction (μ_f = 0.2) extends failure depths to ~2 km, consistent with elastic thickness estimates. We also compare the predicted sense of shear to inferred shear directions from structural mapping efforts and find compatible senses of shear among six of the nine regions that exhibit notable fault offset and/or prevalent inferences of en echelon, duplexes, and strained craters. We expand this regional analysis to a global scale by computing Coulomb failure stress along optimal fault orientations within 15° latitude by 30° longitude gridded cells that span the entire surface. Again, combined diurnal and NSR tidal stress models suggest shear failure conditions should exist within the shallow (< 2 km) icy lithosphere across much of Ganymede. We find that shear failure is limited near the equator due to large compressive NSR stresses, but stresses at mid- to high-latitudes readily promote shear failure along a wide range of fault orientations. These results reflect tidal dynamics assuming a present-day eccentricity for Ganymede of e = 0.0013, however a previous period of high past eccentricity (e = 0.05) may have also allowed for a significant diurnal tidal stress influence on faulting at shallow depths, also possibly at a global scale.