Skip to Main content Skip to Navigation
Journal articles

Scaling seismic fault thickness from the laboratory to the field

Thomas Ferrand 1, 2, 3, 4, * Stefan Nielsen 5 Loic Labrousse 6 Alexandre Schubnel 7 
* Corresponding author
4 Géodynamique - UMR7327
BRGM - Bureau de Recherches Géologiques et Minières (BRGM), ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327 : UMR7327, INSU - CNRS - Institut national des sciences de l'Univers, UO - Université d'Orléans : UMR7327
Abstract : Pseudotachylytes originate from the solidification of frictional melt, which transiently forms and lubricates the fault plane during an earthquake. Here we observe how the pseudotachylyte thickness a scales with the relative displacement D both at the laboratory and field scales, for measured slip varying from microns to meters, over six orders of magnitude. Considering all the data jointly, a bend appears in the scaling relationship when slip and thickness reach ∼1 mm and 100 µm, respectively, i.e. MW > 1. This bend can be attributed to the melt thickness reaching a steady‐state value due to melting dynamics under shear heating, as is suggested by the solution of a Stefan problem with a migrating boundary. Each increment of fault is heating up due to fast shearing near the rupture tip and starting cooling by thermal diffusion upon rupture. The building and sustainability of a connected melt layer depends on this energy balance. For plurimillimetric thicknesses (a > 1 mm), melt thickness growth reflects in first approximation the rate of shear heating which appears to decay in D−1/2 to D−1, likely due to melt lubrication controlled by melt + solid suspension viscosity and mobility. The pseudotachylyte thickness scales with moment M0 and magnitude MW; therefore, thickness alone may be used to estimate magnitude on fossil faults in the field in the absence of displacement markers within a reasonable error margin.
Document type :
Journal articles
Complete list of metadata
Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Saturday, December 26, 2020 - 9:42:12 AM
Last modification on : Wednesday, August 3, 2022 - 4:05:29 AM
Long-term archiving on: : Monday, March 29, 2021 - 4:42:11 PM


Files produced by the author(s)



Thomas Ferrand, Stefan Nielsen, Loic Labrousse, Alexandre Schubnel. Scaling seismic fault thickness from the laboratory to the field. Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2021, 126 (3), pp.e2020JB020694. ⟨10.1029/2020JB020694⟩. ⟨insu-03088354⟩



Record views


Files downloads