Premium
Friction velocity dependence of clay‐rich fault material along a megasplay fault in the Nankai subduction zone at intermediate to high velocities
Author(s) -
Tsutsumi Akito,
Fabbri Olivier,
Karpoff Anne Marie,
Ujiie Kohtaro,
Tsujimoto Atsushi
Publication year - 2011
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 - 10.1029/2011gl049314
Subject(s) - fault gouge , geology , slip (aerodynamics) , shear (geology) , fault (geology) , homogeneous , subduction , deformation (meteorology) , shear zone , seismology , geotechnical engineering , petrology , tectonics , thermodynamics , oceanography , physics
The frictional properties of clay‐rich fault material collected from a megasplay fault within the Nankai accretionary complex were examined in frictional experiments performed at a normal stress of 5 MPa under water‐saturated conditions for slip velocities from 0.0026 to 260 mm/s with >250 mm of displacement. Our results reveal that the fault material can show two stages of velocity weakening behavior: weakening at slow velocities ( v < 2.6 mm/s), characterized by a small degree of friction velocity dependence (the absolute value of ( a − b ) is typically <0.005), and a dramatic weakening at high velocities ( v > 26 mm/s). Such a process of fault weakening may provide important constraints on models of faulting along a megasplay fault. At slip velocities from 0.026 to 2.6 mm/s, there exist both velocity‐weakening and velocity‐strengthening fault materials. The frictional coefficient values, μ , for slow slip velocities ( v = 0.26 mm/s) are relatively low ( μ = 0.28–0.35) for velocity‐strengthening samples compared with velocity‐weakening samples ( μ = 0.38–0.49). Microstructural analyses reveal that velocity‐strengthening samples show homogeneous deformation textures in which the entire gouge layer is deformed, whereas velocity‐weakening materials show evidence of shear localization in which deformation is concentrated along narrow subsidiary shears.