MOONQUAKE-TRIGGERED MASS WASTING PROCESSES ON ICY WORLDS

Intense tectonism is evident on many outer solar system satellites. Some surface regions on icy satellites exhibit ridge-and-trough structures with characteristics suggestive of normal faulting. In some cases, topographic lows between subparallel ridges are sites of textureless material displaying few craters. We consider whether such smooth material can be generated by mass wasting triggered from local seismic shaking. We hypothesize that debris would flow from topographic highs into lows, initially mobilized by moonquake-induced seismic shaking during formation of local tectonic ridges, covering and infilling older terrain. We analyze the feasibility of seismicity to trigger mass movements by measuring fault scarp dimensions to estimate seismic moment magnitudes. The inferred magnitude range is 4.9–8.4, and we use numerical modeling to estimate seismic accelerations resulting from such quakes. This modeled magnitude range implies seismic accelerations exceeding satellite gravitational accelerations, particularly near quake epicenters. Thus, such seismic events could feasibly cause mass wasting to form some fine-scale smooth surfaces observed on at least three icy satellites: Ganymede, Europa, and Enceladus.