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Pure and Applied Geophysics

, Volume 168, Issue 12, pp 2427–2449 | Cite as

Earthquake Rupture at Focal Depth, Part II: Mechanics of the 2004 M2.2 Earthquake Along the Pretorius Fault, TauTona Mine, South Africa

  • V. Heesakkers
  • S. Murphy
  • D. A. Lockner
  • Z. RechesEmail author
Article

Abstract

We analyze here the rupture mechanics of the 2004, M2.2 earthquake based on our observations and measurements at focal depth (Part I). This event ruptured the Archean Pretorius fault that has been inactive for at least 2 Ga, and was reactivated due to mining operations down to a depth of 3.6 km depth. Thus, it was expected that the Pretorius fault zone will fail similarly to an intact rock body independently of its ancient healed structure. Our analysis reveals a few puzzling features of the M2.2 rupture-zone: (1) the earthquake ruptured four, non-parallel, cataclasite bearing segments of the ancient Pretorius fault-zone; (2) slip occurred almost exclusively along the cataclasite-host rock contacts of the slipping segments; (3) the local in-situ stress field is not favorable to slip along any of these four segments; and (4) the Archean cataclasite is pervasively sintered and cemented to become brittle and strong. To resolve these observations, we conducted rock mechanics experiments on the fault-rocks and host-rocks and found a strong mechanical contrast between the quartzitic cataclasite zones, with elastic-brittle rheology, and the host quartzites, with damage, elastic–plastic rheology. The finite-element modeling of a heterogeneous fault-zone with the measured mechanical contrast indicates that the slip is likely to reactivate the ancient cataclasite-bearing segments, as observed, due to the strong mechanical contrast between the cataclasite and the host quartzitic rock.

Keywords

Deformation Modulus Witwatersrand Basin Axial Fracture South African Minis Gouge Zone 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

We are in debt to many people and organizations. Foremost to Gerrie van Aswegen of ISS International who guided and advised us throughout this entire study. This work was not possible without the invaluable help and support by Hannes Moller, Pieter van Zyl, Rob Burnet, and many other workers in TauTona mine and ISSI. We greatly appreciate the help in underground work by Tom Dewers, Amir Allam, Kate Moore, and Matthew Zechmeister of University of Oklahoma, Reginald Domoney, Selwyn Adams, and Curnell Campher, of the University of Western Cape, South Africa, Amie Lucier of Stanford University, and Malcolm Johnston, US Geological Survey. This work could not be completed without the important advice, suggestions and encouragement by the NELSAM team of Tom Jordan, Malcolm Johnston, Mark Zoback, TC Onstott, as well as Hiroshi Ogasawara, Ritsumeikan University, Japan, and Uli Harms, GFZ, Germany. Many thanks to AngloGoldAshanti for the permission to work in the TauTona mine and the generous logistic support. The thoughtful comments of two anonymous reviewers significantly improved the manuscript. This work was supported by the National Science Foundation under Grant no. 0409605 (NELSAM project), and the drilling grant by ICDP (DAFSAM project). Other sponsors of this work include US Geological survey, AngloGoldAshanti, ISS International, and National Research Foundation (NRF).

References

  1. Armstrong, R.A., Compston, W., Retief, E.A., Williams, I.S., and Welke, H.J. (1991), Zircon ion microprobe studies bearing on the age and evolution of the Witwatersrand triad, Precambrian Res., 53, 243–266.Google Scholar
  2. Barton, C.A., and Zoback, M.D. (1994), Stress perturbations associated with active faults penetrated by boreholes: possible evidence for near-complete stress drop and a new technique for stress magnitude measurement, J. Geophys. Res. 99, 9373–9390.Google Scholar
  3. Boettcher, M.S., McGarr, A., and Johnston, M. (2009), Extension of GutenbergRichter distribution to M w −1.3, no lower limit in sight, Geophys. Res. Lett., 36.Google Scholar
  4. Byerlee, J.D. (1967), Frictional characteristics of granite under high confining pressure, J. Geophys. Res. 72, 3639–3648.Google Scholar
  5. Byerlee, J. (1993), Model for episodic high-pressure water in fault zones before earthquakes, Geology, 21, 303–306.Google Scholar
  6. Cartwright, P., and Walker, G. (2000), In-situ stress measurement, 83 level shaft pillar area, TauTona mine, AngloGold.Google Scholar
  7. Cook, N.G.W., (1963), The seismic location of rockbursts, In: Proc. Rock Mechanics Symposium, 5th, Pergamon Press, Oxford, p. 493.Google Scholar
  8. Di Toro, G., and Pennacchioni, G. (2004), Superheated friction-induced melts in zoned pseudotachylytes within the Adamello tonalites (Italian Southern Alps), J. Structural Geol., 26, 1783–1801.Google Scholar
  9. Dor, O., Reches, Z., and van Aswegen, G. (2001), Fault zones associated with the Matjhabeng earthquake 1999, South Africa: Rockburst and Seismicity in Mines, RaSiM5 (Proceedings), South African Inst. Mining and Metallurgy, pp 109–112.Google Scholar
  10. Faulkner, D.R., Mitchell, T.M., Healy, D., and Heap, M.J. (2006), Slip on “weak” faults by the rotation of regional stress in the fracture damage zone, Nature, 444, 922–925.Google Scholar
  11. Gay N.C. (1976), Fracture growth around openings in large blocks of rock subjected to uniaxial and biaxial compression. Int. J. Rock Mech. Min. Sci. & Geomech. Abstr. 13, 231–243.Google Scholar
  12. Gay N.C., and Ortlepp W.D. (1979), Anatomy of a mining-induced fault zone, Bull. geol. Soc. Am. 90, 47–58.Google Scholar
  13. Gibowicz, S.J., and Kijko, A. (1994), An Introduction to Mining Seismology, Academic Press, San Diego.Google Scholar
  14. Gibson, R.L., Reimold, W.U., Phillips, D., and Layer, P.W. (2000), Ar 40 /Ar 39 constraints on the age of metamorphism in the Witwatersrand Supergroup, Vredefort Dome (South Africa), South African J. Geol., 103, 175–190.Google Scholar
  15. Healy, D. (2008), Damage patterns, stress rotations and pore fluid pressures in strike-slip fault zones, J. Geophys. Res., 113.Google Scholar
  16. Heesakkers, V., Murphy, S., Lockner, D.A., and Reches, Z., (2011) (Part I). Earthquake Rupture at Focal Depth, Part I: structure and rupture of the Pretorius Fault, TauTona Mine, South Africa (this volume).Google Scholar
  17. Katz, O., Gilbert, M.C., Reches, Z., and Roegiers, J.C. (2001), Mechanical properties of the Mount Scott Granite, Wichita Mountains, Oklahoma, Oklahoma Geology Notes, 61, 28–34.Google Scholar
  18. Katz, O., and Reches, Z. (2004), Microfracturing, damage, and failure of brittle granites, J. Geophys. Res., 109, B1, B01206.Google Scholar
  19. Kirsch, G. (1898), Die Theorie der Elastizitat und die Bedurfnisse der Festigkeitslehre. VDI Z, 42, 707.Google Scholar
  20. Lockner, D.A. (1998), A generalized law for brittle deformation of Westerly granite, J. Geophys. Res., 103, 5107–5123.Google Scholar
  21. Lucier, A.M., Zoback, M.D., Heesakkers, V., Reches, Z., and Murphy, S.K. (2009), Constraining the far-field in situ stress state near a deep South African gold mine, Int. J. Rock Mechanics Mining Sci., 46, 555–567.Google Scholar
  22. McGarr, A., (1984), Some applications of seismic source mechanism studies to assessing underground hazard: Rockburst and Seismicity in Mines, In: Symp. Ser. No. 6, South African. Inst. Min. Metal., (ed Gay, N.C. and Wainwright, E.H.), Johannesburg, 199–208.Google Scholar
  23. McGarr, A. (1992), Moment tensors of ten Witwatersrand mine tremors, Pure Appl. Geophys., 139, 781–800.Google Scholar
  24. McGarr, A. (2002), Control of strong ground motion of mining-induced earthquakes by the strength of the seismogenic rock mass. J. the South African Inst. Mining Metallurgy. 102, 225–229.Google Scholar
  25. McGarr, A., and Gay, N.C. (1978), State of Stress in the Earth’s Crust, Ann. Rev. Earth Planetary Sci., 6, 405–436.Google Scholar
  26. McGarr, A., Pollard, D.D., Gay, N.C., and Ortlepp, W.D. (1979a), Observations and Analysis of Structures in Exhumed Mine-induces Faults, Proceedings of Conference VIII: Analysis of Actual Fault Zones in Bedrock, US Geol. Survey, Menlo Park, Open file Rep. 79–1239, 101–120.Google Scholar
  27. McGarr, A., Spottiswoode, S.M., Gay, N.C., and Ortlepp, W.D. (1979b), Observations relevant to seismic driving stress, stress drop, and efficiency, J. Geophys. Res., 84, B5, 2251–2261.Google Scholar
  28. McGarr, A., Spottiswoode, S.M., and Gay, N.C., (1975), Relationship of mine tremors to induced stresses and to rock properties in the focal region, Bull. Seism. Soc. Am., 65, 981–993.Google Scholar
  29. Mendecki, A.J., Seismic Monitoring in Mines, (ed. Mendecki, A.J.) (Chapman and Hall, London 1997).Google Scholar
  30. Ogasawara, H., T. Yanagidani, and M. Ando (editors), (2002), Seismogenic Process Monitoring, Balkema, Rotterdam.Google Scholar
  31. Ortlepp W.D. (1978), The mechanism of a rockburst, Proc. 19th U.S. Rock Mechanics Symp., Reno, Nevada, 476–483.Google Scholar
  32. Peska, P., and Zoback, M.D. (1995), Compressive and tensile failure of inclined well bores and determination of in situ stress and rock strength, J. Geophys. Res., 100, 12791–12811.Google Scholar
  33. Reches, Z. (1979), Deformation of a foliated medium, Tectonophysics, 57, 119–129.Google Scholar
  34. Reches, Z. (2006), Building a natural earthquake laboratory at focal depth, Scientific Drilling 3, 30–33.Google Scholar
  35. Reches, Z., Baer, G., and Hatzor, Y. (1992), Constraints on the Strength of the Upper Crust from Stress Inversion of Fault Slip Data, J. Geophys. Res., 97(B9), 12481–12493.Google Scholar
  36. Reches, Z., and Ito, H., Scientific drilling of active faults: past and future, In Scientific Drillings Continental Scientific Drilling A Decade of Progress, and Challenges for the Future (ed. Harms, U., Koeberl, C., and Zoback, M.D.) (Springer 2007), 235–258.Google Scholar
  37. Reches, Z., and Lockner, D.A. (1994), Nucleation and growth of faults in brittle rocks, J. Geophys. Res., 99, 18159–18173.Google Scholar
  38. Reches, Z., and Lockner, D.A. (2010). Fault weakening and earthquake instability by powder lubrication, Nature, 467, 452–456.Google Scholar
  39. Rice, J.R. (1992), Fault stress states, pore pressure distributions, and the weakness of the San Andreas Fault, In Fault mechanics and transport properties of rock (ed. Evans, B., and W. Tf), London, Academic press, pp. 475–504.Google Scholar
  40. Richardson, E., and Jordan, T.H. (2002), Seismicity in Deep Gold Mines of South Africa: Implications for Tectonic Earthquakes, Bull. Seism. Soc. Am., 92, 1766–1782.Google Scholar
  41. Robb, L.J., Charlesworth, E.G., Drennan, G.R., Gibson, R.L., and Tongu, E.L. (1997), Tectono-metamorphic setting and paragenetic sequence of Au-U mineralisation in the Archaean Witwatersrand Basin, South Africa, Australian J. Earth Sci., 44, 353–371.Google Scholar
  42. Sibson, R.H. (1994), Crustal stress, faulting and fluid flow: geological Society, London, Special Publications, 78, 69–84.Google Scholar
  43. Spottiswoode, S.M. (1980), Source mechanism studies on Witwatersrand seismic events, Ph.D Thesis, University of the Witwatersrand, Johannesburg.Google Scholar
  44. Spottiswoode, S.M., and McGarr, A. (1975), Source parameters of tremors in a deep-level gold mine, Bull. Seism. Soc. Am., 65, 93–112.Google Scholar
  45. Tembe, S., Lockner, D., and Wong, T.F. (2009), Constraints on the stress state of the San Andreas Fault with analysis based on core and cuttings from San Andreas Fault Observatory at Depth (SAFOD) drilling phases 1 and 2, J. Geophys. Res., 114.Google Scholar
  46. Tsutsumi, A., and Shimamoto, T. (1997), High-velocity Frictional Properties of Gabbro, Geophys. Res. Lett., 24.Google Scholar
  47. van Aswegen, G., Reches, Z., Jordan, T.H., and Ben-Zion, Y. (2002), Drilling Active Faults in South Africa Mines: An in-situ laboratory to study earthquake and fault mechanics, Am. Geophy. Union, Fall Meeting 2002, Abstract U72B-0021.Google Scholar
  48. Yabe, Y., Philipp, J., Nakatani, M., Morema G., Naoi, M., Kawakata, H., Igarashi, T., Dresen, G., Ogasawara, H., and Jaguars, (2009), Observation of numerous aftershocks of an Mw 1.9 earthquake with an AE network installed in a deep gold mine in South Africa. Earth Planets Space, 61, e49–e52.Google Scholar
  49. Yamamoto, K., Sato, N., and Yabe, Y. (2000), Stress state around the Nojima fault estimated from core measurements, Proceedings of the Int. Workshop on the Nojima Fault Core and Borehole Data Analysis, 239–246.Google Scholar
  50. Zoback, M.D., Barton, C.A., Brudy, M., Castillo, D.A., Finkbeiner, T., Grollimund, B.R., Moos, D.B., Peska, P., Ward, C.D., Wiprut, D.J., and Hudson, J.A. (2003), Determination of stress orientation and magnitude in deep wells, Int. J. Rock Mechanics and Mining Sci., 40, 1049–1076.Google Scholar
  51. Zoback, M.D., Zoback, M.L., Mount, V.S., Suppe, J., Eaton, J.P., Healy, J.H., Oppenheimer, D.H., Reasenberg, P.A., Jones, L.M., Raleigh, C.B., Wong, I.G., Scotti, O., and Wentworth, C.M. (1987), New evidence on the state of stress of the San Andreas fault system, Science, 238, 1105–1111.Google Scholar

Copyright information

© AOCS (outside the USA) 2011

Authors and Affiliations

  • V. Heesakkers
    • 1
    • 2
  • S. Murphy
    • 3
  • D. A. Lockner
    • 4
  • Z. Reches
    • 1
    Email author
  1. 1.School of Geology and Geophysics, University of OklahomaNormanUSA
  2. 2.Chevron ETCHoustonUSA
  3. 3.AngloGold AshantiCarletonvilleSouth Africa
  4. 4.US Geological SurveyMenlo ParkUSA

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