Publication Date:
2017-04-04
Description:
In a recent work on the problem of sliding surfaces under the presence
of frictional melt (applying in particular to earthquake fault dynamics),
we derived from first principles an expression for the steady state
friction compatible with experimental observations. Building on the
expressions of heat and mass balance obtained in the above study for
this particular case of Stefan problem (phase transition with a migrating
boundary) we propose here an extension providing the full time-dependent
solution (including the weakening transient after pervasive melting
has started, the effect of eventual steps in velocity and the final
decelerating phase). A system of coupled equations is derived and
solved numerically. The resulting transient friction and wear evolution
yield a satisfactory fit (1) with experiments performed under variable
sliding velocities (0.9-2 m/s) and different normal stresses (0.5-20
MPa) for various rock types and (2) with estimates of slip weakening
obtained from observations on ancient seismogenic faults that host
pseudotachylite (solidified melt). The model allows to extrapolate
the experimentally observed frictional behavior to large normal stresses
representative of the seismogenic Earth crust (up to 200 MPa), high
slip rates (up to 9 m/s) and cases where melt extrusion is negligible.
Though weakening distance and peak stress vary widely, the net breakdown
energy appears to be essentially independent of either slip velocity
and normal stress. In addition, the response to earthquake-like slip
can be simulated, showing a rapid friction recovery when slip rate
drops. We discuss the properties of energy dissipation, transient
duration, velocity weakening, restrengthening in the decelerating
final slip phase and the implications for earthquake source dynamics.
Description:
S.N. and G.D.T. were supported by a European Research Council Starting
Grant Project (acronym USEMS) and by a Progetti di Eccellenza Fondazione
Cassa di Risparmio di Padova e Rovigo. We are grateful to Nick Beeler
(and to an anonymous referee) for their constructive reviews and their
help to improve the clarity of the manuscript.
Description:
Published
Description:
B10301
Description:
3.1. Fisica dei terremoti
Description:
JCR Journal
Description:
open
Keywords:
Friction
;
Melt
;
Earthquake dynamics
;
fault mechanics
;
04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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