Premium
Clay‐clast aggregates: A new textural evidence for seismic fault sliding?
Author(s) -
Boutareaud Sébastien,
Calugaru DanGabriel,
Han Raehee,
Fabbri Olivier,
Mizoguchi Kazuo,
Tsutsumi Akito,
Shimamoto Toshihiko
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl032554
Subject(s) - fault gouge , geology , slip (aerodynamics) , shear (geology) , geotechnical engineering , pore water pressure , fault (geology) , clay minerals , mineralogy , petrology , seismology , thermodynamics , physics
To determine the processes responsible for slip‐weakening in clayey gouge zones, rotary‐shear experiments were conducted at seismic slip rates (equivalent to 0.9 and 1.3 m/s) at 0.6 MPa normal stress on a natural clayey gouge for saturated and non‐saturated initial conditions. The mechanical behavior of the simulated faults shows a reproducible slip‐weakening behavior, whatever initial moisture conditions. Examination of gouge obtained at the residual friction stage in saturated and non‐saturated initial conditions allows the definition of two types of microstructures: a foliated type reflecting strain localization, and a non‐foliated type composed of spherical aggregates. Friction experiments demonstrate that liquid‐vapor transition of water within gouge due to frictional heating has a high capacity to explain the formation of spherical aggregates in the first meters of displacement. This result suggests that the occurrence of spherical aggregates in natural clayey fault gouges can constitute a new textural evidence for shallow depth pore water phase transition at seismic slip velocity and consequently for past seismic fault sliding.