Stick-slip and creep behavior in lubricated granular material: Insights into the brittle-ductile transition

• Published in: Geophysical research letters 2014-05, Vol.41 (10), p.3471-3477
• Main Authors: Reber, Jacqueline E., Hayman, Nicholas W., Lavier, Luc L.
• Format: Article
• Language: English
• Subjects: brittle-ductile transition; creep; Deformation; Disks; Ductile brittle transition; Experiments; Interstitials; Localization; Position (location); Rheology; Shear zone; Silicones; stick lip; Strain; strain transient
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2014GL059832

Crustal deformation can occur via stick‐slip events, viscous creep, or strain transients at variable rates. Here we explore such strain transients with physical experiments comprising a quasi‐two‐dimensional shear zone with elastic, acrylic discs and interstitial viscous silicone. Experiments of solely elastic discs produce stick‐slip events and an overall (constant volume) strengthening. The addition of the viscous silicone enhances localization but does not greatly change the overall pattern of strengthening. It does, however, damp the stick‐slip events, leading to transient, creep‐like behavior that approaches the behavior of a Maxwell body. There is no gradual transition from frictional to viscous deformation with increasing amounts of silicone, suggesting that the mixed rheology is in effect as soon as an interstitial fluid is present. Our experiments support the hypothesis that a possible cause for strain transients in nature is an interstitial viscous phase in shear zones. Key Points Frictional shear zones with a weak viscous phase can cause strain transients Deformation localization is strong in a lubricated granular media The viscosity of the weak phase governs the damping of the stick‐slip behavior