Earth, Planets and Space

, Volume 56, Issue 12, pp 1177–1184 | Cite as

On the geoelectric structure of major strike-slip faults and shear zones

  • Martyn Unsworth
  • Paul A. Bedrosian
Open Access


Magnetotelluric imaging of the San Andreas Fault has shown that seismically-active segments are characterized by a zone of low resistivity in the upper crust. Similar resistivity features are observed on other major strike-slip faults, and may have a common origin in a region of fractured rock, partially or fully saturated with groundwater. Other strike-slip faults show possible zones of reduced resistivity in the mid and lower crust that may be related to zones of ductile shear. Additional MT surveys are required to elucidate the role of fluids in controlling the seismic behaviour of major faults, both in and below the seismogenic zone. A set of synthetic inversions show that MT data is sensitive to the geoelectric structure of a shear zone at mid-crustal depths.

Key words

Magnetotellurics shear zones strike-slip faults earthquake cycle San Andreas Fault 


  1. Anderson, J. L., R. H. Osborne, and D. E. Palmer, Cataclastic rocks of the San Gabriel Fault—an expression of deformation at deeper crustal levels in the San Andreas Fault Zone, Tectonophysics, 98, 209–251, 1983.CrossRefGoogle Scholar
  2. Archie, G. E., The electrical resistivity log as an aid in determining some reservoir characteristics, Trans. Am. Inst. Min. Metall. Pet. Eng., 146, 54–62, 1942.Google Scholar
  3. Bai, D. and M. Meju, Deep structure of the Longling-Ruili fault underneath Ruili basin near the eastern Himalayan syntaxis: Insights from MT imaging, Tectonophysics, 364, 135–146, 2003.CrossRefGoogle Scholar
  4. Bakun, W. H. and A. G. Lindh, The Parkfield, California, Earthquake Prediction Experiment, Science, 229, 619–624, 1985.CrossRefGoogle Scholar
  5. Bedrosian, P. A., M. J. Unsworth, and G. D. Egbert, Magnetotelluric imaging of the creeping segment of the San Andreas Fault near Hollister, Geophys. Res. Lett., 29, 1506, doi:10.1029/2001GL012119, 2002.CrossRefGoogle Scholar
  6. Bedrosian, P. A., M. J. Unsworth, G. D. Egbert, and C. H. Thurber, Geophysical images of the creeping segment of the San Andreas Fault: Implications for the role of crustal fluids in the earthquake process, Tectonophysics, 385, doi:10.1016/j.tecto.2004.02.010, 2004.Google Scholar
  7. Blandpied, M. L., D. A. Lockner, and J. D. Byerlee, An earthquake mechanism based on rapid sealing of faults, Nature, 358, 574–576, 1992.CrossRefGoogle Scholar
  8. Byerlee, J., Model for episodic flow of high pressure water in fault zones before earthquakes, Geology, 21, 303–306, 1993.CrossRefGoogle Scholar
  9. Chester, F. M., J. P. Evans, and R. L. Biegel, Internal structure and weakening mechanisms of the San Andreas Fault, J. Geophys. Res., 98, 771–786, 1993.CrossRefGoogle Scholar
  10. Clark, M. K. and L. H. Royden, Topographic ooze: Building the Eastern margin of Tibet by lower crustal flow, Geology, 28, 703–706, 2000.CrossRefGoogle Scholar
  11. Eberhart-Phillips, D., V. F. Labson, W. D. Stanley, A. J. Michael, and B. D. Rodriguez, Preliminary velocity and resistivity models of the Loma Prieta earthquake region, Geophys. Res. Lett., 17, 1235–1238, 1990.CrossRefGoogle Scholar
  12. Electromagnetic Research Group for the Active Fault, Low electrical resistivity along an active fault, J. Geomag. Geoelectr., 34, 103–127, 1982.CrossRefGoogle Scholar
  13. Hickman, S., M. Zoback, and W. Ellsworth, Introduction to special section: Preparing for the San Andreas Fault Observatory at Depth, Geophys. Res. Lett., 31, L12S01, doi:10.1029/2004GL020688, 2004.Google Scholar
  14. Hoffman-Rothe, A., O. Ritter, and C. Janssen, Correlation of electrical conductivity an structural damage at a major strike-slip fault in Northern Chile, J. Geophys. Res., 109, doi:10.1029/2004JB003030, 2004.Google Scholar
  15. Irwin, W. P. and I. Barnes, Effect of geologic structure and metamorphic fluids on seismic behavior of the San Andreas Fault system in central and northern California, Geology, 3,, 1975.CrossRefGoogle Scholar
  16. Janssen, C., A. Hoffman-Rothe, S. Tauber, and H. Wilke, Internal structure of the pre-cordilleran fault system (Chile)—insights from structural and geophysical observations, J. Structural Geology, 24, 123–143, 2002.CrossRefGoogle Scholar
  17. Johnson, P. A. and T. V. McEvilly, Parkfield seismicity: Fluid-driven?, J. Geophys. Res., 100, 12,937–12,950, 1995.CrossRefGoogle Scholar
  18. Jones, A. G., R. D. Kurtz, D. E. Boerner, J. A. Craven, McG. W. Neice, D. I. Gough, J. M. DeLaurier, and R. G. Ellis, Electromagnetic constraints on strike-slip fault geometry—The Fraser River Fault System, Geology, 20, 561, 1992a.CrossRefGoogle Scholar
  19. Jones, A. G., Electrical conductivity of the continental lower crust, in Continental Lower Crust, edited by D. M. Fountain, R. J. Arculus, and R. W. Kay, Elsevier, Amsterdam, Chapter 3: pp. 81–143, 1992b.Google Scholar
  20. Mackie, R. L., D. W. Livelybrooks, T. R. Madden, and J. C. Larsen, A magnetotelluric investigation of the San Andreas Fault at Carrizo Plain, California, Geophys. Res. Lett., 24, 1847–1850, 1997.CrossRefGoogle Scholar
  21. Madden, T. R., G. A. LaTorraca, and S. K. Park, Electrical conductivity variations around the Palmdale section of the San Andreas Fault Zone, J. Geophys. Res., 98, 795–808, 1993.CrossRefGoogle Scholar
  22. Mazella, A. and H. F. Morrison, Electrical resistivity variations associated with earthquakes on the San Andreas Fault, Science, 185, 855–857, 1974.CrossRefGoogle Scholar
  23. Mitsuhata, Y., Y. Ogawa, M. Mishina, T. Kono, T. Yokokura, and T. Uchida, Electromagnetic heterogeneity of the seismogenic region of 1962 M6.5 Northern Miyagi Earthquake, northeastern Japan, Geophys. Res. Lett., 28(23), 4371–4374, 2001.CrossRefGoogle Scholar
  24. Nadeau, R. M., W. Foxall, and T. V. McEvilly, Clustering and periodic recurrence of microearthquakes on the San Andreas Fault at Parkfield, California, Science, 267, 503–507, 1995.CrossRefGoogle Scholar
  25. Ogawa, Y., M. Mishina, T. Goto, H. Satoh, N. Oshiman, T. Kasaya, Y. Takahashi, T. Nishitani, S. Sakanaka, M. Uyeshima, Y. Takahashi, Y. Honkura, and M. Matsushima, Magnetotelluric imaging of fluids in intraplate earthquake zones, NE Japan back arc, Geophys. Res. Lett., 28(19), 3741–3744, 2001.CrossRefGoogle Scholar
  26. Ritter, O., T. Ryberg, U. Weckmann, A. Hoffmann-Rothe, A. Abueladas, Z. Garfunkel, and DESERT Research Group, Geophysical images of the Dead Sea Transform in Jordan reveal an impermeable barrier for fluid flow, Geophys. Res. Lett., 30(14), 1741, doi:10.1029/2003GL017541, 2003.CrossRefGoogle Scholar
  27. Ritter, O., A. Hoffman-Rothe, P. A. Bedrosian, U. Weckmann, and V. Haak, Electrical conductivity images of active and fossil fault zones, in Microstuctural Evolution and Physical Properties in High Strain Zones, Geological Society of London Special Publications, 2004 (in press).Google Scholar
  28. Rodi, W. and R. L. Mackie, Nonlinear conjugate gradients algorithm for 2-D magnetotelluric inversion, Geophysics, 66, 174–187, 2001.CrossRefGoogle Scholar
  29. Sun, J., G. Jin, D. Bai, and L. Wang, Sounding of electrical structure of the crust and upper mantle along the eastern border of Qinghai-Tibet plateau and its tectonic significance, Science in China (Series D), 46, 243–253, 2003.CrossRefGoogle Scholar
  30. Tank, S. B., Y. Honkura, Y. Ogawa, N. Oshiman, M. K. Tunçer, M. Matsushima, C. Çelik, E. Tolak, and A. M. Işikara, Resistivity structure in the western part of the fault rupture zone associated with the 1999 İzmit earthquake and its seismogenic implication, Earth Planets Space, 55, 437–442, 2003.CrossRefGoogle Scholar
  31. Tank, S. B., Y. Honkura, Y. Ogawa, M. Matsushima, N. Oshiman, M. K. Tuncer, C. Celik, E. Tolak, and A. M. Isikara, Magnetotelluric imaging of the fault rupture area of the 1999 Izmit (Turkey) earthquake, Physics of the Earth and Planetary Interiors, 2004 (in press).Google Scholar
  32. Tapponnier, P., Xu Zhiqin, F. Roger, B. Meyer, N. Arnaud, G. Wittlinger, and Y. Jingsui, Oblique stepwise rise and growth of the Tibetan Plateau, Science, 294, 1671–1677, 2001.CrossRefGoogle Scholar
  33. Thurber, C. and S. Roecker, Two-dimensional seismic image of the San Andreas Fault in the Northern Gabilan Range, central California: Evidence for fluids in the fault zone, Geophys. Res. Lett., 24, 1591–1594, 1997.CrossRefGoogle Scholar
  34. Thurber, C., S. Roecker, K. Roberts, M. Gold, L. Powell, and K. Rittger, Earthquake locations and three-dimensional fault zone structure along the creeping section of the San Andreas Fault near Parkfield, CA: Preparing for SAFOD, Geophys. Res. Lett., 31, doi:10.1029/2002GL016004, 2003.Google Scholar
  35. Unsworth, M. J., G. D. Egbert, and J. R. Booker, High Resolution electromagnetic imaging of the San Andreas Fault in Central California, J. Geophys. Res., 104, 1131–1150, 1999.CrossRefGoogle Scholar
  36. Unsworth, M. J., M. Eisel, G. D. Egbert, W. Siripunarvaporn, and P. A. Bedrosian, Along-strike variations in the structure of the San Andreas Fault at Parkfield, California, Geophys. Res. Lett., 27, 3021–3024, 2000.CrossRefGoogle Scholar
  37. Unsworth, M. J., W. Wei, A. G. Jones, S. Li, P. A. Bedrosian, J. R. Booker, S. Jin, and M. Deng, Crustal and upper mantle structure of Northern Tibet imaged with magnetotelluric data, J. Geophys. Res., 109, doi:10.1029/2002JB002305, 2004.Google Scholar
  38. Wannamaker, P. E., Affordable magnetotellurics: Interpretation in natural environments, in Three-dimensional Electromagnetics, edited by M. Oristaglio and B. Spies, Geophys. Devel. Ser., no. 7, Soc. Expl. Geophys., pp. 349–374, 1999.CrossRefGoogle Scholar
  39. Wannamaker, P. E., Comment on “The petrologic case for a dry lower crust” by B. W D. Yardley and J. W Valley, J. Geophys. Res., 105(B3), 6057–6064, 10.1029/1999JB900324, 2000.CrossRefGoogle Scholar
  40. Wannamaker, P. E., G. R. Jiracek, J. A. Stodt, T. G. Caldwell, V. Gonzalez, J. McKnight, and A. D. Porter, Fluid generation and pathways beneath an active compressional orogen, the New Zealand Southern Alps, inferred from magnetotelluric data, J. Geophys. Res., 107, 2001JB000186, 2002.Google Scholar
  41. Yardley, B. W. D. and J. W. Valley, The petrologic case for a dry lower crust, J. Geophys. Res., 102, 12173, 1997.CrossRefGoogle Scholar

Copyright information

© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2004

Authors and Affiliations

  1. 1.University of AlbertaEdmontonCanada
  2. 2.GeoForschungsZentrumPotsdamGermany

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