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Fault zone fabric and fault weakness

Abstract

Geological and geophysical evidence suggests that some crustal faults are weak1,2,3,4,5,6 compared to laboratory measurements of frictional strength7. Explanations for fault weakness include the presence of weak minerals4, high fluid pressures within the fault core8,9 and dynamic processes such as normal stress reduction10, acoustic fluidization11 or extreme weakening at high slip velocity12,13,14. Dynamic weakening mechanisms can explain some observations; however, creep and aseismic slip are thought to occur on weak faults, and quasi-static weakening mechanisms are required to initiate frictional slip on mis-oriented faults, at high angles to the tectonic stress field. Moreover, the maintenance of high fluid pressures requires specialized conditions15 and weak mineral phases are not present in sufficient abundance to satisfy weak fault models16, so weak faults remain largely unexplained. Here we provide laboratory evidence for a brittle, frictional weakening mechanism based on common fault zone fabrics. We report on the frictional strength of intact fault rocks sheared in their in situ geometry. Samples with well-developed foliation are extremely weak compared to their powdered equivalents. Micro- and nano-structural studies show that frictional sliding occurs along very fine-grained foliations composed of phyllosilicates (talc and smectite). When the same rocks are powdered, frictional strength is high, consistent with cataclastic processes. Our data show that fault weakness can occur in cases where weak mineral phases constitute only a small percentage of the total fault rock and that low friction results from slip on a network of weak phyllosilicate-rich surfaces that define the rock fabric. The widespread documentation of foliated fault rocks along mature faults in different tectonic settings and from many different protoliths4,17,18,19 suggests that this mechanism could be a viable explanation for fault weakening in the brittle crust.

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Figure 1: Example of a foliated low-angle normal fault.
Figure 2: Friction experiments.
Figure 3: Frictional properties of fault rocks and powders made from them.
Figure 4: Comparison between solid-foliated and powder sliding surfaces in L3.

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References

  1. Zoback, M. D. et al. New evidence on the state of stress of the San Andreas fault system. Science 238, 1105–1111 (1987)

    Article  ADS  CAS  Google Scholar 

  2. Holdsworth, R. E. Weak faults—rotten cores. Science 303, 181–182 (2004)

    Article  CAS  Google Scholar 

  3. Chiaraluce, L., Chiarabba, C., Collettini, C., Piccinini, D. & Cocco, M. Architecture and mechanics of an active low-angle normal fault: Alto Tiberina Fault, northern Apennines, Italy. J. Geophys. Res. 112 B10310 10.1029/2007JB005015 (2007)

    Article  ADS  Google Scholar 

  4. Moore, D. E. & Rymer, M. Talc-bearing serpentinites and the creeping section of the San Andreas fault. Nature 448 795–797 10.1038/nature06064 (2007)

    Article  ADS  CAS  PubMed  Google Scholar 

  5. Brune, J. N., Henyey, T. L. & Roy, R. F. Heat flow, stress, and rate of slip along the San Andreas Fault, California. J. Geophys. Res. 74, 3821–3827 (1969)

    Article  ADS  Google Scholar 

  6. Wintsch, R. P., Christoffersen, R. & Kronenberg, A. K. Fluid-rock reaction weakening of fault zones. J. Geophys. Res. 100, 13021–13032 (1995)

    Article  ADS  CAS  Google Scholar 

  7. Byerlee, J. D. Friction of rocks. Pure Appl. Geophys. 116, 615–629 (1978)

    Article  ADS  Google Scholar 

  8. Rice, J. R. in Fault Mechanics and Transport Properties of Rocks (eds Evans, B. & Wong, T.-f.) 475–503 (Academic Press, 1992)

    Google Scholar 

  9. Faulkner, D. R., Mitchell, T. M., Healy, D. & Heap, M. J. Slip on ‘weak’ faults by the rotation of regional stress in the fracture damage zone. Nature 444, 922–925 (2004)

    Article  ADS  Google Scholar 

  10. Ampuero, J.-P. & Ben-Zion, Y. Cracks, pulses and macroscopic asymmetry of dynamic rupture on a bimaterial interface with velocity-weakening friction. Geophys. J. Int. 173, 674–692 (2008)

    Article  ADS  Google Scholar 

  11. Melosh, H. J. Dynamical weakening of faults by acoustic fluidization. Nature 279, 601–606 (1996)

    Article  ADS  Google Scholar 

  12. Di Toro, G., Hirose, T., Nielsen, S., Pennacchioni, G. & Shimamoto, T. Natural and experimental evidence of melt lubrication of faults during earthquakes. Science 311, 647–649 (2006)

    Article  ADS  CAS  Google Scholar 

  13. Wibberley, C. A. J. & Shimamoto, T. Earthquake slip weakening and asperities explained by thermal pressurization. Nature 436, 689–692 (2005)

    Article  ADS  CAS  Google Scholar 

  14. Boutareaud, S. et al. Clay-clast aggregates: A new textural evidence for seismic fault sliding? Geophys. Res. Lett. 35 L05302 10.1029/2007GL032554 (2008)

    Article  ADS  Google Scholar 

  15. Scholz, C. H. The Mechanics of Earthquakes and Faulting 2nd edn, 1–508 (Cambridge University Press, 2002)

    Book  Google Scholar 

  16. Carpenter, B. M., Marone, C. & Saffer, D. Frictional behavior of materials in the 3D SAFOD volume. Geophys. Res. Lett. 36 L05302 10.1029/2008GL036660 (2009)

    Article  ADS  Google Scholar 

  17. Vrolijk, P. & van der Pluijm, B. A. Clay gouge. J. Struct. Geol. 21, 1039–1048 (1999)

    Article  ADS  Google Scholar 

  18. Faulkner, D. R., Lewis, A. C. & Rutter, E. H. On the internal structure and mechanics of large strike-slip faults: field observations from the Carboneras fault, southeastern Spain. Tectonophysics 367, 235–251 (2003)

    Article  ADS  Google Scholar 

  19. Jefferies, S. P. et al. The nature and importance of phyllonite development in crustal-scale fault cores: an example from the Median Tectonic Line, Japan. J. Struct. Geol. 28, 220–235 (2006)

    Article  ADS  Google Scholar 

  20. Scholz, C. H. Evidence for a strong San Andreas fault. Geology 28, 163–166 (2000)

    Article  ADS  Google Scholar 

  21. Townend, J. & Zoback, M. D. How faulting keeps the crust strong. Geology 28, 399–402 (2000)

    Article  ADS  Google Scholar 

  22. Collettini, C. & Sibson, R. H. Normal faults, normal friction? Geology 29, 927–930 (2001)

    Article  ADS  Google Scholar 

  23. Noda, H., Dunham, E. M. & Rice, J. R. Earthquake ruptures with thermal weakening and the operation of major faults at low overall stress levels. J. Geophys. Res. 114 B07302 10.1029/2008JB006143 (2009)

    Article  ADS  Google Scholar 

  24. Collettini, C., Viti, C., Smith, S. A. F. & Holdsworth, R. E. The development of interconnected talc networks and weakening of continental low-angle normal faults. Geology 37, 567–570 (2009)

    Article  ADS  CAS  Google Scholar 

  25. Beeler, N. M., Tullis, T. E. & Blanpied, M. L. &. Weeks, J. D. Frictional behavior of large displacement experimental faults. J. Geophys. Res. 101, 8697–8715 (1996)

    Article  ADS  Google Scholar 

  26. Marone, C. Laboratory-derived friction laws and their application to seismic faulting. Annu. Rev. Earth Planet. Sci. 26, 643–696 (1998)

    Article  ADS  CAS  Google Scholar 

  27. Evans, J. P. & Chester, F. M. Fluid rock interaction in faults of the San Andreas system: inferences from San Gabriel fault-rock geochemistry and microstructures. J. Geophys. Res. 100, 13007–13020 (1995)

    Article  ADS  CAS  Google Scholar 

  28. Bos, B., Peach, C. J. & Spiers, C. J. Frictional-viscous flow of simulated fault gouge caused by the combined effects of phyllosilicates and pressure solution. Tectonophysics 327, 173–194 (2000)

    Article  ADS  CAS  Google Scholar 

  29. Niemeijer, A. R. & Spiers, C. J. Velocity dependence of strength and healing behaviour in simulated phyllosilicate-bearing fault gouge. Tectonophysics 427, 231–253 (2006)

    Article  ADS  Google Scholar 

  30. Imber, J. et al. in The Internal Structure of Fault Zones: Implications for Mechanical and Fluid-Flow Properties (eds Wibberley, C. A. J. et al.) Vol. 299, 151–173 (Geological Society of London Special Publication, 2008)

    Google Scholar 

  31. Niemeijer, A. R. & Spiers, C. J. A microphysical model for strong velocity weakening in phyllosilicate-bearing fault gouges. J. Geophys. Res. 112 B10405 10.1029/2007JB005008 (2007)

    Article  ADS  Google Scholar 

  32. Saffer, D. M., Frye, K. F., Marone, C. & Mair, K. Laboratory results indicating complex and potentially unstable frictional behavior of smectite clay. Geophys. Res. Lett. 28, 2297–2300 (2001)

    Article  ADS  CAS  Google Scholar 

  33. Shea, W. T. J. & Kronenberg, A. K. Strength and anisotropy of foliated rocks with varied mica contents. J. Struct. Geol. 15, 1097–1121 (1993)

    Article  ADS  Google Scholar 

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Acknowledgements

We thank I. Faoro for cutting the samples and J. P. Ampuero, D. Faulkner, R. Holdsworth and S. Smith for discussions. This research was motivated in part by stimulating discussions with P. Montone, M. Barchi and M. Cocco. We gratefully acknowledge funding by NSF grants OCE-0196462 EAR-0510182 and an INGV-DPC S5 M. Barchi grant. A.N. was supported in part by the ERC St. G. Nr.205175 USEMS project.

Author Contributions C.C., A.N. and C.M. designed the study. A.N. and C.C. carried out the experiments. A.N., C.C. and C.M. conducted the data analysis. C.C. and C.V. carried out the microstructural studies. C.V. did TEM and mineralogical characterization. All the authors contributed to the writing.

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Correspondence to Cristiano Collettini.

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Collettini, C., Niemeijer, A., Viti, C. et al. Fault zone fabric and fault weakness. Nature 462, 907–910 (2009). https://doi.org/10.1038/nature08585

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