title: G: Fracture energy, friction and dissipation in earthquakes.
abstract: Recent estimates of fracture energyG'in earthquakes show a power-law dependence with slipuwhich can be summarized asG'∝uawhereais a positive real slightly larger than one. For cracks with sliding friction, fracture energy can be equated toGf: the post-failure integral of the dynamic weakening curve. If the dominant dissipative process in earthquakes is friction,G'andGfshould 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 energyGfis similar to the seismological estimates, withGfandG'being comparable over most of the slip range. However,Gfappears to saturate after several meters of slip, while in most of the reported earthquake sequences,G'appears to increase further and surpassesGfat large magnitudes. We analyze several possible causes of such discrepancy, in particular, additional off-fault damage in large natural earthquakes.
authors.affiliation: Istituto Nazionale di Geofisica e Vucanologia, Rome, Italy ; Durham University, Earth Sciences, Durham, UK.
authors.forename: S
authors.initials: S
authors.lastname: Nielsen
authors.affiliation: Istituto Nazionale di Geofisica e Vucanologia, Rome, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Spagnuolo
authors.affiliation: Istituto Nazionale di Geofisica e Vucanologia, Rome, Italy ; EPFL, Lausanne, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Violay
authors.affiliation: Istituto Nazionale di Geofisica e Vucanologia, Rome, Italy ; Department of Geology, University of Otago, Otago, New Zealand.
authors.forename: S
authors.initials: S
authors.lastname: Smith
authors.affiliation: Istituto Nazionale di Geofisica e Vucanologia, Rome, Italy ; School of Earth, Atmospheric and Environmental Sciences, Manchester University, Manchester, UK ; Dipartimento di Geoscienze Address, Università degli Studi di Padova Division, Padova, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Di Toro
authors.affiliation: Istituto Nazionale di Geofisica e Vucanologia, Rome, Italy ; Department of Earth and Environmental Sciences, Universitá degli Studi di Milano Bicocca, Milan, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Bistacchi
keywords: Earthquake scaling; Fracture energy; High velocity friction; Laboratory experiments