Abstract
Tidal walking has been proposed as a mechanism inducing lateral offset on preexisting strike-slip faults on Europa by tidal forcing. We test this hypothesis numerically by modeling a part of Europa's ice shell with an embedded strike-slip fault.
Our model involves two coupled processes: (i) slip at the fault and deformation of the ice shell on the tidal timescale and (ii) thermal evolution of the ice shell on the timescale of tens of thousands of years. The fault is characterized by the Mohr-Coulomb criterion allowing to determine self-consistently the activation depth of the fault.
On the tidal timescale, the ice shell is described by the Maxwell viscoelasticity; on the convection timescale, the ice is treated as a non-Newtonian viscous fluid. We show that tidal walking is capable of producing surface lateral offset of the order of kilometers over 100 thousand years provided that the active part of the fault penetrates the high-viscosity part of the shell.
Such conditions are likely not met for the current amplitude of the tidal forcing and for the estimated ice shell thickness. We show that either larger forcing amplitude (e.g., due to higher eccentricity of the moon) or partial flooding of the fault zone by water from the ocean is required to produce the observed offset.
We demonstrate that thermo-mechanical coupling can significantly enhance the efficiency of tidal walking and we investigate conditions for which the fault's activity can result in observable surface thermal signatures.