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An earthquake instability model based on faults containing high fluid-pressure compartments

Abstract

It has been proposed that large strike-slip faults such as the San Andreas contain water in seal-bounded compartments. Arguments based on heat flow and stress orientation suggest that in most of the compartments, the water pressure is so high that the average shear strength of the fault is less than 20 MPa. We propose a variation of this basic model in which most of the shear stress on the fault is supported by a small number of compartments where the pore pressure is relatively low. As a result, the fault gouge in these compartments is compacted and lithified and has a high undisturbed strength. When one of these locked regions fails, the system made up of the neighboring high and low pressure compartments can become unstable. Material in the high fluid pressure compartments is initially underconsolidated since the low effective confining pressure has retarded compaction. As these compartments are deformed, fluid pressure remains nearly unchanged so that they offer little resistance to shear. The low pore pressure compartments, however, are overconsolidated and dilate as they are sheared. Decompression of the pore fluid in these compartments lowers fluid pressure, increasing effective normal stress and shear strength. While this effect tends to stabilize the fault, it can be shown that this dilatancy hardening can be more than offset by displacement weakening of the fault (i.e., the drop from peak to residual strength). If the surrounding rock mass is sufficiently compliant to produce an instability, slip will propagate along the fault until the shear fracture runs into a low-stress region. Frictional heating and the accompanying increase in fluid pressure that are suggested to occur during shearing of the fault zone will act as additional destabilizers. However, significant heating occurs only after a finite amount of slip and therefore is more likely to contribute to the energetics of rupture propagation than to the initiation of the instability.

We present results of a one-dimensional dynamic Burridge-Knopoff-type model to demonstrate various aspects of the fluid-assisted fault instability described above. In the numerical model, the fault is represented by a series of blocks and springs, with fault rheology expressed by static and dynamic friction. In addition, the fault surface of each block has associated with it pore pressure, porosity and permeability. All of these variables are allowed to evolve with time, resulting in a wide range of phenomena related to fluid diffusion, dilatancy, compaction and heating. These phenomena include creep events, diffusion-controlled precursors, triggered earthquakes, foreshocks, aftershocks, and multiple earthquakes. While the simulations have limitations inherent to 1-D fault models, they demonstrate that the fluid compartment model can, in principle, provide the rich assortment of phenomena that have been associated with earthquakes.

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References

  1. Andrews, D. J. (1989),Mechanics of Fault Junctions, J. Geophys. Res.94, 9389–9397.

    Google Scholar 

  2. Ben-Zion, Y., andRice, J. R. (1993),Earthquake Failure Sequences along a Celluar Fault Zone in a Three-dimensional Elastic Solid Containing Asperity and Nonasperity Regions, J. Geophys. Res.98, 14, 109–14, 131.

    Google Scholar 

  3. Ben-Zion, Y., andRice, J. R. (1995),Slip Patterns and Earthquake Populations along Different Classes of Faults in Elastic Solids, J. Geophys. Res.100, 12959–12983.

    Google Scholar 

  4. Blanpied, M. L., Lockner, D. A., andByerlee, J. D. (1992).An Earthquake Mechanism Based on Rapid Sealing of Faults, Nature358, 574–576.

    Google Scholar 

  5. Blanpied, M. L., Lockner, D. A., andByerlee, J. D. (1995),Frictional Slip of Granite at Hydrothermal Conditions, J. Geophys. Res.100, 13045–13064.

    Google Scholar 

  6. Burridge, R., andKnopoff, L. (1967),Model and Theoretical Seismicity, Bull. Seismol. Soc. Am.57, 341–371.

    Google Scholar 

  7. Byerlee, J. D. (1978),Friction of Rocks, Pure and Appl. Geophys.116, 615–626.

    Google Scholar 

  8. Byerlee, J. D. (1990),Friction, Overpressure and Fault Normal Compression, Geophys. Res. Lett.17, 2109–2112.

    Google Scholar 

  9. Byerlee, J. D. (1992),The Change in Orientation of Subsidiary Shears near Faults Containing Pore Fluid under High Pressure, Tectonophysics211, 295–303.

    Google Scholar 

  10. Byerlee, J. D. (1993),Model for Episodic Flow of High Pressure Water in Fault Zones before Earthquakes, Geology21, 303–306.

    Google Scholar 

  11. Byerlee, J. D., andSavage, J. C. (1992),Coulomb Plasticity within the Fault Zone, Geophys. Res. Lett.19, 2341–2344.

    Google Scholar 

  12. Carlson, J. M., andLanger, J. S. (1989),Mechanical Model of an Earthquake, Phys. Rev. A40, 6470–6484.

    Google Scholar 

  13. Carlson, J. M., Langer, J. S., Shaw, B., andTang, C. (1991),Intrinsic Properties of a Burridge-Knopoff Model of a Fault, Phys. Rev. A44, 884–897.

    Google Scholar 

  14. Dieterich, J. H. (1972),Time-dependent Friction as a Possible Mechanism for Aftershocks, J. Geophys. Res.77, 3771–3781.

    Google Scholar 

  15. Dieterich, J. H. (1978),Time-dependent Friction and the Mechanics of Stick Slip, Pure and Appl. Geophys.116, 790–806.

    Google Scholar 

  16. Fredrich, J. T., andEvans, B.,Strengh recovery along simulated faults by solution transfer processes. In 33rd U.S. Rock Mechanics Symposium (eds. Tillerson, J. R., and Warersik, W. R.) (Balkema, Rotterdam 1992) pp. 121–130.

    Google Scholar 

  17. Hickman, S. H. (1991),Stress in the Lithosphere and the Strength of Active Faults, Rev. Geophys., IUGG Report, 759–775.

  18. Johnston, M. J. S., Linde, A. T., Gladwin, M. T., andBorcherdt, R. D. (1987),Fault Failure with Moderate Earthquakes, Tectonophysics144, 189–206.

    Google Scholar 

  19. Lachenbruch, A. H. (1980),Frictional Heating, Fluid Pressure, and the Resistance to Fault Motion, J. Geophys. Res.85, 6097–6112.

    Google Scholar 

  20. Lachenbruch, A. H., andSass, J. H. (1980),Heat Flow and Energetics of the San Andreas Fault Zone, J. Geophys. Res.85, 6185–6222.

    Google Scholar 

  21. Li, Y.-G., Vidale, J. E., Aki, K., Marone, C. J., andLee, W. H. K. (1994),Fine Structure of the Landers Fault Zone: Segmentation and the Rupture Process, Science265, 367–370.

    Google Scholar 

  22. Lockner, D. A.,Rock failure. InAGU Handbook of Physical Constants (ed. Ahrens, T. J.) (Am. Geophys. Union, Washington, D.C. 1995)3–10, 127–147.

    Google Scholar 

  23. Lockner, D. A., andByerlee, J. D. (1993),How Geometric Constraints Contribute to the Weakness of Mature Faults, Nature363, 250–252.

    Google Scholar 

  24. Lockner, D. A., andByerlee, J. D. (1994),Dilatancy in Hydraulically Isolated Faults and the Suppression of Instability, Geophys. Res. Lett.21, 2353–2356.

    Google Scholar 

  25. Lockner, D. A., Okubo, P. G., andDieterich, J. H. (1982),Containment of Stick-slip Failures on a Simulated Fault by Pore Fluid Injection, Geophys. Res. Lett.9, 801–804.

    Google Scholar 

  26. Marone, C., andKilgore, B. (1993),Scaling of the Critical Slip Distance for Seismic Faulting with Shear Strain in Fault Zones, Nature362, 618–621.

    Google Scholar 

  27. Marone, C., Raleigh, C. B., andScholz, C. H. (1990),Frictional Behavior and Constitutive Modelling of Simulated Fault Gouge, J. Geophys. Res.95, 7007–7025.

    Google Scholar 

  28. Moore, D. E., Lockner, D. A., andByerlee, J. D. (1994),Reduction of Permeability in Granite at Elevated Temperatures, Science265, 1558–1561.

    Google Scholar 

  29. Moore, D. E., Summer, R., andByerlee, J. D. (1986),The Effects of Sliding Velocity on the Frictional and Physical Properties of Heated Fault Gouge, Pure and Appl. Geophys.124, 31–52.

    Google Scholar 

  30. Morrow, C., Lockner, D., andByerlee, J.,Velocity-and time-dependent transients in simulated fault gouge, InProc. of Int. Symp. on Engineering in Complex Rock Formations (Int. Soc. Rock Mech., Beijing 1986).

    Google Scholar 

  31. Morrow, C., Radney, B., andByerlee, J.,Frictional strength and the effective pressure law of montmorillonite and illite clays. InFault Mechanics and Transport Properties of Rocks (eds. Evans, B., and Wong, T.-f.) (Academic Press, London 1992) pp. 69–88.

    Google Scholar 

  32. Morrow, C. A., andByerlee, J. D. (1989),Experimental Studies of Compaction and Dilatancy during Frictional Sliding on Faults Containing Gouge, J. Struct. Geol.11, 815–825.

    Google Scholar 

  33. Nur, A., andBooker, J. R. (1972),Aftershocks Caused by Pore Fluid Flow? Science175, 885–887.

    Google Scholar 

  34. Reinen, L. A., Weeks, J. D., andTullis, T. E. (1994),The Frictional Behavior of Lizardite and Antigorite Serpentinites: Experiments, Constitutive Models, and Implications for Natural Foult, Pure and Appl. Geophys.143, 317–358.

    Google Scholar 

  35. Rice, J. R.,Fault stress states, pore pressure distributions, and the weakness of the San Andreas faults. InFault Mechanics and Transport Properties of Rocks (eds. Evans, B., and Wong, T.-f.) (Academic Press, London 1992), pp. 475–503.

    Google Scholar 

  36. Rice, J. R. (1993),Spatio-temporal Complexity of Slip on a Fault, J. Geophys. Res.98, 9885–9907.

    Google Scholar 

  37. Robertson, E. C. (1983),Relationship of Fault Displacement to Gouge and Breccia Thickness, Trans. A.I.M.E.35, 1426–1432.

    Google Scholar 

  38. Rudnicki, J. W., andChen, C.-H. (1988),Stabilization of Rapid Frictional Slip on a Weakening Fault by Dilatant Hardening, J. Geophys. Res.93, 4745–4757.

    Google Scholar 

  39. Scholz, C. H., Sykes, L. R., andAggarwal, Y. P. (1973),Earthquake Prediction: A Physical Basis, Science181, 803–810.

    Google Scholar 

  40. Sibson, R. H. (1982),Fault Zone Models, Heat Flow, and the Depth Distribution of Earthquakes in the Continental Crust of the United States, Bull. Seismol. Soc. Am.72, 151–163.

    Google Scholar 

  41. Sleep, N. H., andBlanpied, M. L. (1992),Creep, Compaction and the Weak Rheology of Major Faults, Nature359, 687–692.

    Google Scholar 

  42. Sleep, N. H., andBlanpied, M. L. (1994),Ductile Creep and Compaction: A Mechanism for Transiently Increasing Fluid Pressure in Mostly Sealed Fault Zones, Pure and Appl. Geophys.143, 9–40.

    Google Scholar 

  43. Walther, J. V. Fluid dynamics during progressive regional metamorphism. InThe Role of Fluids In Crustal Processes (ed. Council, N. R.) (National Academy Press, Washington, D.C. 1990) pp. 64–71.

    Google Scholar 

  44. Wesson, R. L. (1988),Dynamics of Fault Creep, J. Geophys. Res.93, 8929–8951.

    Google Scholar 

  45. Zoback, M. D. et al. (1987),New Evidence on the State of Stress of the San Andreas Fault System, Science238, 1105–1111.

    Google Scholar 

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Lockner, D.A., Byerlee, J.D. An earthquake instability model based on faults containing high fluid-pressure compartments. PAGEOPH 145, 717–745 (1995). https://doi.org/10.1007/BF00879597

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Key words

  • Earthquake cycle
  • overpressure
  • fluid compartments
  • dynamic earthquake model