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- Title
Tidal Walking on Europa's Strike‐Slip Faults—Insight From Numerical Modeling.
- Authors
Sládková, K.; Souček, O.; Kalousová, K.; Běhounková, M.
- 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. Plain Language Summary: The icy surface of Jupiter's moon Europa is scarred by a large number of cracks along which a lateral motion of the ice shell was reconstructed. To explain this observation, a model of "tidal walking" was proposed: The tidal forces periodically open and close the crack, and, at the same time, they push parts of the ice shell along the crack. This lateral motion is facilitated by tensional opening of the crack but is suppressed or stopped when the crack is under compression. By this process, a significant displacement between the two sides of the crack can accumulate. In this paper, we study this process with a numerical model. We show that while tidal walking is probably ineffective with current tidal forcing, it could have been acting earlier in Europa's evolution when its orbit was more eccentric than at present. We further investigate thermal signatures of the strike‐slip motions and discuss conditions for which the heat flux anomalies could be observed above currently active Europan strike‐slip faults. Key Points: We numerically study the tidally induced strike‐slip motions on Europa's faults and their geomorphological and thermal signaturesThe model couples tidal deformation and fault slip determined by the Mohr‐Coulomb criterion with thermal evolution of the ice shellObservable lateral offset and heat flux anomaly can be produced especially if the fault penetrates the highly viscous part of shell
- Subjects
HYPOTHESIS; TOMOGRAPHY; HOMOGENEITY; GEOMORPHOLOGY; MICROWAVES
- Publication
Journal of Geophysical Research. Planets, 2020, Vol 125, Issue 8, p1
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2019JE006327