Scaling in natural and laboratory earthquakes

• Published in: Geophysical research letters 2016-02, Vol.43 (4), p.1504-1510
• Main Authors: Nielsen, S., Spagnuolo, E., Smith, S. A. F., Violay, M., Di Toro, G., Bistacchi, A.
• Format: Article
• Language: English
• Subjects: Activation; Approximation; Complexity; Earthquake damage; earthquake scaling; Earthquakes; Energy; Estimates; Fault zones; fracture energy; Fracture mechanics; Fracture toughness; Friction; high‐velocity friction experiments; Laboratories; Laboratory experiments; Lubrication; Mechanical stimuli; Power law; Scaling; Seismic activity; Seismic phenomena; Seismology; Shear; Shear stress; Slip; Structural damage; Structures; Variability
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL067490

Laboratory experiments reproducing seismic slip conditions show extreme frictional weakening due to the activation of lubrication processes. Due to a substantial variability in the details of the weakening transient, generalization of experimental results and comparison to seismic observations have not been possible so far. Here we show that during the weakening, shear stress τ is generally well matched by a power law of slip u in the form τ∝u−α (with 0.35 < α < 0.6). The resulting fracture energy Gf can be approximated by a power law in some aspects in agreement with the seismological estimates G′. It appears that Gf and G′ are comparable in the range 0.01 < u < 0.3 m. However, G′ surpasses Gf at larger slips: at u≈10 m, G′≈108 and Gf≈106. Possible interpretations of this misfit involve the complexity of damage and weakening mechanisms within mature fault zone structures. Key Points Dynamic friction weakening scales as a power law of slip The generalized weakening form explains the observed scaling of earthquake fracture energy In large earthquakes, dominating dissipation is not friction but rather plastic, off‐fault strain