Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.p11f..06s&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #P11F-06
Physics
5422 Ices, 5475 Tectonics (8149), 5770 Tidal Forces, 6280 Saturnian Satellites, 8168 Stresses: General
Scientific paper
Cassini observations of the south polar region of Saturn's moon Enceladus revealed four large linear fractures, or "tiger stripes," associated with anomalous heat flow and active plumes. These features are thought to be active faults along which tidally induced strike-slip and/or open-close tectonic motions occur, similar to motions inferred for some fractures on Europa. These motions are likely a result of tidally induced stresses exerted on a satellite during its daily elliptical orbital cycle around its parent body. When resolved onto potentially active fault planes, tidal shear stresses drive strike-slip motions, while normal stresses control a fault's frictional resistance to failure. Accounting for both stress contributions, the Coulomb failure criterion holds that shear failure will occur on optimally oriented fault planes when the applied shear stress exceeds the frictional resistance of a fault. Thus, Coulomb stress is a measure of a fault's potential to store stress in the form of fault locking (when normal stresses dominate), or to release stress in the form of fault slip (when shear stresses dominate). We resolve shear and normal tidal stresses onto the tiger stripe fault system and also account for normal stress at depth due to the overburden pressure. We compute Coulomb stress failure conditions to assess failure direction, frequency, and location throughout the Enceladus orbital cycle and find that the entire tiger stripe system is capable of sustaining periods of fault locking (stress accumulation) near periapse and fault displacement (shear slip) near apoapse. We integrate these stresses into a 3D time-dependent fault dislocation model to evaluate tectonic displacements and stress variations at depth. Depending on the sequence of imposed stress accumulation and release, which varies as a function of fault location and orientation, frictional coefficient, and fault depth, we estimate that approximately 0.5 m of horizontal strike-slip displacement (both right and left-lateral) are possible during a tiger stripe fault slip episode. These analyses of tidal stress accumulation and subsequent fault displacement may help explain observed plume activity and temperature anomalies at Enceladus's south polar region as related to shear heating and vapor release.
Pappalardo Robert T.
Smith-Konter Bridget R.
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