Estimating the Magnitude of Cyclic Slip on Strike‐Slip faults on Europa

• Published in: Journal of geophysical research. Planets 2020-07, Vol.125 (7), p.no-no
• Main Author: Hammond, N. P.
• Format: Article
• Language: English
• Subjects: Coefficient of friction; Displacement; Europa; fault mechanics; Fractures; geodynamics; Geological faults; Heating; Ice; Ice cover; icy satellite; Icy satellites; Jupiter; Melting; Moon; Shear modulus; Sliding; Slip; Stresses; strike‐slip fault; tectonics; Thermal cycling; Tides
• ISSN: 2169-9097; 2169-9100
• DOI: 10.1029/2019JE006170

Strike‐slip faults on Europa may slide back and forth in response to diurnal tidal stresses, which could generate significant frictional heating near the surface. Previous shear heating models assumed fault sliding rates a priori, without showing how the sliding rate is connected to the resolved stresses acting on the fault. Here, I calculate the cyclic displacement along tidally driven faults. I use a Mohr‐Coulomb failure criterion to determine the frictional failure depth, which varies throughout the tidal cycle. The displacement on the fault is calculated assuming an elastic broken plate model. The magnitude of cyclic displacements along a fault depends upon the coefficient of friction and the shear modulus of the ice shell. If Europa's ice shell is weak, diurnal tidal stress can cause faults on Europa to slide back and forth by ~0.1 to 2 m each cycle. Such large amounts of cyclic slip may be enough to frictionally heat the ice and potentially produce near‐surface melting. If Europa's ice shell has the strength of intact ice, faults become less responsive to cyclic tidal stresses and would only slide 0.01 to 0.2 m per cycle. Plain Language Summary Europa, Jupiter's icy moon, has many fractures and faults in its ice shell. As the moon gets stretched and squeezed by tidal forces from Jupiter, faults may slide back and forth, generating a significant amount of shear heating. I show that tidal stresses can cause faults to slide back and forth by up to 2 m each orbit. In some cases, frictional heating can cause faults to slide fast enough to generate near‐surface melting and potentially water pockets only a few 100 m below the surface. Key Points If Europa's surface is weak, cyclic tidal stresses can cause back‐and‐forth slip of up to 0.1–2 m on strike‐slip faults Shear heating caused by cyclic slip of ~1 m may be sufficient to generate near‐surface melting