TY  - JOUR
A1  - Schuck, Bernhard
A1  - Schleicher, Anja Maria
A1  - Janssen, Christoph
A1  - Toy, Virginia G.
A1  - Dresen, Georg
T1  - Fault zone architecture of a large plate-bounding strike-slip fault
BT  - A case study from the Alpine Fault, New Zealand
JF  - Solid Earth
N2  - New Zealand's Alpine Fault is a large, platebounding strike-slip fault, which ruptures in large (M-w > 8) earthquakes. We conducted field and laboratory analyses of fault rocks to assess its fault zone architecture. Results reveal that the Alpine Fault Zone has a complex geometry, comprising an anastomosing network of multiple slip planes that have accommodated different amounts of displacement. This contrasts with the previous perception of the Alpine Fault Zone, which assumes a single principal slip zone accommodated all displacement. This interpretation is supported by results of drilling projects and geophysical investigations. Furthermore, observations presented here show that the young, largely unconsolidated sediments that constitute the footwall at shallow depths have a significant influence on fault gouge rheological properties and structure.
KW  - san andreas fault
KW  - thickness-displacement relationships
KW  - central south island
KW  - Ion-Beam (FIB)
KW  - internal structure
KW  - hanging wall
KW  - Fluid Flow
KW  - frictional properties
KW  - weakening mechanisms
KW  - strain localization
Y1  - 2020
U6  - https://doi.org/10.5194/se-11-95-2020
SN  - 1869-9529
VL  - 11
IS  - 1
SP  - 95
EP  - 124
PB  - Copernicus Publications
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Döhmann, Maximilian J.E.A.
A1  - Brune, Sascha
A1  - Nardini, Livia
A1  - Rybacki, Erik
A1  - Dresen, Georg
T1  - Strain Localization and Weakening Processes in Viscously Deforming Rocks
BT  - Numerical Modeling Based on Laboratory Torsion Experiments
JF  - Journal of geophysical research : JGR
N2  - Localization processes in the viscous lower crust generate ductile shear zones over a broad range of scales affecting long‐term lithosphere deformation and the mechanical response of faults during the seismic cycle. Here we use centimeter‐scale numerical models in order to gain detailed insight into the processes involved in strain localization and rheological weakening in viscously deforming rocks. Our 2‐D Cartesian models are benchmarked to high‐temperature and high‐pressure torsion experiments on Carrara marble samples containing a single weak Solnhofen limestone inclusion. The models successfully reproduce bulk stress‐strain transients and final strain distributions observed in the experiments by applying a simple, first‐order softening law that mimics rheological weakening. We find that local stress concentrations forming at the inclusion tips initiate strain localization inside the host matrix. At the tip of the propagating shear zone, weakening occurs within a process zone, which expands with time from the inclusion tips toward the matrix. Rheological weakening is a precondition for shear zone localization, and the width of this shear zone is found to be controlled by the degree of softening. Introducing a second softening step at elevated strain, a high strain layer develops inside the localized shear zone, analogous to the formation of ultramylonite bands in mylonites. These results elucidate the transient evolution of stress and strain rate during inception and maturation of ductile shear zones.
KW  - dislocation creep
KW  - torsion
KW  - 2-D numerical model
KW  - rheological weakening
KW  - two phase aggregates
KW  - strain localization
Y1  - 2018
U6  - https://doi.org/10.1029/2018JB016917
SN  - 0148-0227
SN  - 2169-9356
VL  - 124
IS  - 1
SP  - 1120
EP  - 1137
PB  - Union
CY  - Washington, DC
ER  -