TY - JOUR
T1 - Evolution of Elastic and Mechanical Properties During Fault Shear
T2 - The Roles of Clay Content, Fabric Development, and Porosity
AU - Kenigsberg, Abby R.
AU - Rivière, Jacques
AU - Marone, Chris
AU - Saffer, Demian M.
N1 - Funding Information:
We thank S. Swavely for technical help in the laboratory and Parisa Shokouhi and Charles Ammon for key discussions. We also thank and acknowledge the work of Karissa Rosenberger, Michael Underwood, and Peter Vrolijk for their compositional analysis of the IODP samples used in this study. Finally, we thank two anonymous reviewers and associate editor Yves Bernabe, for the very extremely helpful reviews and suggestions. This research used samples provided by the International Ocean Discovery Program (IODP). Funding for this research was provided by the NSF U.S. Science Support Program (Post expedition award), GDL Foundation, DOE geothermal program (DOE EERE DE-EE0006762), and the NSF Geophysics program (NSF awards EAR-1215856, EAR-1520760, and EAR-1547286/1547441. All data available Penn State ScholarSphere (https://scholarsphere.psu.edu/).
Funding Information:
We thank S. Swavely for technical help in the laboratory and Parisa Shokouhi and Charles Ammon for key discussions. We also thank and acknowledge the work of Karissa Rosenberger, Michael Underwood, and Peter Vrolijk for their compositional analysis of the IODP samples used in this study. Finally, we thank two anonymous reviewers and associate editor Yves Bernabe, for the very extremely helpful reviews and suggestions. This research used samples provided by the International Ocean Discovery Program (IODP). Funding for this research was provided by the NSF U.S. Science Support Program (Post expedition award), GDL Foundation, DOE geothermal program (DOE EERE DE‐EE0006762), and the NSF Geophysics program (NSF awards EAR‐1215856, EAR‐1520760, and EAR‐1547286/1547441. All data available Penn State ScholarSphere ( https://scholarsphere.psu.edu/ ).
Publisher Copyright:
©2020. American Geophysical Union. All Rights Reserved.
PY - 2020/3/1
Y1 - 2020/3/1
N2 - Phyllosilicates weaken faults due to the formation of shear fabrics. Although the impacts of clay abundance and fabric on frictional strength, sliding stability, and porosity of faults are well studied, their influence on elastic properties is less known, though they are key factors for fault stiffness. We document the role that fabric and consolidation play in elastic properties and show that smectite content is the most important factor determining whether fabric or porosity controls the elastic response of faults. We conducted a suite of shear experiments on synthetic smectite-quartz fault gouges (10–100 wt% smectite) and sediment incoming to the Sumatra subduction zone. We monitored Vp, Vs, friction, porosity, shear and bulk moduli. We find that mechanical and elastic properties for gouges with abundant smectite are almost entirely controlled by fabric formation (decreasing mechanical and elastic properties with shear). Though fabrics control the elastic response of smectite-poor gouges over intermediate shear strains, porosity is the primary control throughout the majority of shearing. Elastic properties vary systematically with smectite content: High smectite gouges have values of Vp ~ 1,300–1,800 m/s, Vs ~ 900–1,100 m/s, K ~ 1–4 GPa, and G ~ 1–2 GPa, and low smectite gouges have values of Vp ~ 2,300–2,500 m/s, Vs ~ 1,200–1,300 m/s, K ~ 5–8 GPa, and G ~ 2.5–3 GPa. We find that, even in smectite-poor gouges, shear fabric also affects stiffness and elastic moduli, implying that while smectite abundance plays a clear role in controlling gouge properties, other fine-grained and platy clay minerals may produce similar behavior through their control on the development of fabrics and thin shear surfaces.
AB - Phyllosilicates weaken faults due to the formation of shear fabrics. Although the impacts of clay abundance and fabric on frictional strength, sliding stability, and porosity of faults are well studied, their influence on elastic properties is less known, though they are key factors for fault stiffness. We document the role that fabric and consolidation play in elastic properties and show that smectite content is the most important factor determining whether fabric or porosity controls the elastic response of faults. We conducted a suite of shear experiments on synthetic smectite-quartz fault gouges (10–100 wt% smectite) and sediment incoming to the Sumatra subduction zone. We monitored Vp, Vs, friction, porosity, shear and bulk moduli. We find that mechanical and elastic properties for gouges with abundant smectite are almost entirely controlled by fabric formation (decreasing mechanical and elastic properties with shear). Though fabrics control the elastic response of smectite-poor gouges over intermediate shear strains, porosity is the primary control throughout the majority of shearing. Elastic properties vary systematically with smectite content: High smectite gouges have values of Vp ~ 1,300–1,800 m/s, Vs ~ 900–1,100 m/s, K ~ 1–4 GPa, and G ~ 1–2 GPa, and low smectite gouges have values of Vp ~ 2,300–2,500 m/s, Vs ~ 1,200–1,300 m/s, K ~ 5–8 GPa, and G ~ 2.5–3 GPa. We find that, even in smectite-poor gouges, shear fabric also affects stiffness and elastic moduli, implying that while smectite abundance plays a clear role in controlling gouge properties, other fine-grained and platy clay minerals may produce similar behavior through their control on the development of fabrics and thin shear surfaces.
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U2 - 10.1029/2019JB018612
DO - 10.1029/2019JB018612
M3 - Article
AN - SCOPUS:85082310534
VL - 125
JO - Journal of Geophysical Research
JF - Journal of Geophysical Research
SN - 0148-0227
IS - 3
M1 - e2019JB018612
ER -