G: Fracture energy, friction and dissipation in earthquakes

Nielsen, S.; Spagnuolo, E.; Violay, M.; Smith, S.; Toro, G.; Bistacchi, A.

Abstract

Recent estimates of fracture energy G ′ in earthquakes show a power-law dependence with slip u which can be summarized as G ′ ∝ u a where a is a positive real slightly larger than one. For cracks with sliding friction, fracture energy can be equated to G f : the post-failure integral of the dynamic weakening curve. If the dominant dissipative process in earthquakes is friction, G ′ and G f should be comparable and show a similar scaling with slip. We test this hypothesis by analyzing experiments performed on various cohesive and non-cohesive rock types, under wet and dry conditions, with imposed deformation typical of seismic slip (normal stress of tens of MPa, target slip velocity > 1 m/s and fast accelerations ≈ 6.5 m/s2). The resulting fracture energy G f is similar to the seismological estimates, with G f and G ′ being comparable over most of the slip range. However, G f appears to saturate after several meters of slip, while in most of the reported earthquake sequences, G ′ appears to increase further and surpasses G f at large magnitudes. We analyze several possible causes of such discrepancy, in particular, additional off-fault damage in large natural earthquakes.

Citation

Nielsen, S., Spagnuolo, E., Violay, M., Smith, S., Toro, G., & Bistacchi, A. (2016). G: Fracture energy, friction and dissipation in earthquakes. Journal of Seismology, 20(4), 1187-1205. https://doi.org/10.1007/s10950-016-9560-1

• Journal Article Type: Article
• Acceptance Date: Feb 15, 2016
• Online Publication Date: Mar 31, 2016
• Publication Date: Oct 1, 2016
• Deposit Date: May 4, 2016
• Publicly Available Date: May 5, 2016
• Journal: Journal of Seismology
• Print ISSN: 1383-4649
• Electronic ISSN: 1573-157X
• Publisher: Springer
• Peer Reviewed: Peer Reviewed
• Volume: 20
• Issue: 4
• Pages: 1187-1205
• DOI: https://doi.org/10.1007/s10950-016-9560-1
• Public URL: https://durham-repository.worktribe.com/output/1383012