Frictional measurements were made on natural fault gouge at seismic slip rates using a
high-speed rotary-shear apparatus to study effects of slip velocity, acceleration,
displacement, normal stress, and water content. Thermal-, mechanical-, and fluid-flowcoupled
FEM models and microstructure observations were implemented to analyze
experimental results. Slightly sheared starting material (Unit 1) and a strongly sheared
and foliated gouge (Unit 2) are produced when frictional heating is insignificant and the
coefficient of sliding friction is 0.4 to 0.6. A random fabric gouge with rounded
prophyroclasts (Unit 3) and an extremely-fine, microfoliated layer (Unit 4) develop
when significant frictional heating occurs at greater velocity and normal stress, and the
coefficient of sliding friction drops to approximately 0.2. The frictional behavior at
coseismic slip can be explained by thermal pressurization and a temperature-dependent
constitutive relation, in which the friction coefficient is proportional to 1/T and increases
with temperature (temperature-strengthening) at low temperature conditions and decreases with temperature (temperature-weakening) at higher temperature conditions.
The friction coefficient, normal stress, pore pressure, and temperature within the gouge
layer vary with position (radius) and time, and they depend largely on the frictional
heating rate. The critical displacement for dynamic weakening is approximately 10 m or
less, and can be understood as the displacement required to form a localized slip zone
and achieve a steady-state temperature condition.
The temporal and spatial evolution of hydromechanical properties of recovered from
the Nankai Trough (IODP NanTroSEIZE Stage 1 Expeditions) have been investigated
along different stress paths, which simulate the natural conditions of loading during
sedimentation, underthrusting, underplating, overthrusting, and exhumation in
subduction systems. Porosity evolution is relatively independent of stress path, and the
sediment porosity decreases as the yield surface expands. In contrast, permeability
evolution depends on the stress path and the consolidation state, e.g., permeability
reduction by shear-enhanced compaction occurs at a greater rate under triaxialcompression
relative to uniaxial-strain and isotropic loading. In addition, experimental
yielding of sediment is well described by Cam-Clay model of soil mechanics, which is
useful to better estimate the in-situ stress, consolidation state, and strength of sediment in
nature.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-12-8648 |
| Date | 2010 December 1900 |
| Creators | Kitajima, Hiroko |
| Contributors | Chester, Frederick M., Chester, Judith S. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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