Nonplanar Faults: Mechanics of Slip and Off-fault Damage
Stress interactions and sliding characteristics of faults with random fractal waviness in a purely elastic medium differ both qualitatively and quantitatively from those of faults with planar surfaces. With nonplanar fault models, solutions for slip diverge as resolution of the fractal features increases, and the scaling of fault slip with fault rupture dimension becomes nonlinear. We show that the nonlinear scaling of slip and divergence of solutions arise because stresses from geometric interactions at irregularities along nonplanar faults grow with increasing slip and produce backstresses that progressively impede slip. However, in real materials with finite strength, yielding will halt the growth of the interaction stresses, which will profoundly affect slip of nonplanar faults. We infer that in the brittle seismogenic portion of the Earth’s crust, off-fault yielding occurs on pervasive secondary faults. Predicted rates of stress relaxation with distance from major faults with random fractal roughness follow a power-law relationship that is consistent with reported clustering of background seismicity up to 15 kilometers from faults.
Key wordsFaults fault mechanics seismicity fault roughness damage fractal fault slip
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- Brown, S. R. and Scholz, C. H. (1985), Broad bandwidth study of the topography of natural rock surfaces, J. Geophys. Res.-Sol. Earth Planets 90, 2575–2582.Google Scholar
- Candela, T., Renard, F., Bouchon, M., Marsan, D., Schmittbuhl, J., and Voisin, C. (2009), Characterization of fault roughness at various scales: Implications of three-dimensional high resolution topography measurement, Tectonophysics.Google Scholar
- Chester, F., Field guide to the Punchbowl Fault Zone at Devil’s Punchbowl Los Angeles County Park, California (Texas A&M University, Texas 1999).Google Scholar
- Chester , et al. (1996).Google Scholar
- Dieterich, J. H., Richards-Dinger, K., and Smith, D. E. (2008), Large-scale simulations of fault system seismicity. Paper presented at 6th ACES International Workshop on Earthquake Simulation, Cairns, Australia, May 11–16, 2008.Google Scholar
- Hauksson, E. (2009), Spatial Separation of Large Earthquakes, Aftershocks, and Background Seismicity: Analysis of Interseismic and Coseismic Seismicity Patterns in Southern California, Pure Appl. Geophys., Special Frank Evison Issue, in press.Google Scholar
- Peitgen, H., Jürgens, H., and Saupe, D., Chaos and Fractals: New Frontiers of Science (Springer-Verlag, New York 1992).Google Scholar
- Powers, P. M. and Jordan, T. H. (2008), Distribution of seismicity across strike-slip faults in California, EOS Trans. AGU, 89, Fall Meet. Suppl., Abstract S21B–1831.Google Scholar
- Scholz, C. H. and Aviles, C. A. (Eds.), The Fractal Geometry of Faults and Faulting, 147–156 pp. (Am. Geophys. Union, Washington D.C. 1986).Google Scholar
- Smith, D. E. and Dieterich, J. H. (2008), Rate-state modeling of stress relaxation in geometrically complex systems. Paper presented at Seismol. Soc. Am. Annual Meeting, Santa Fe, NM, April 16–18, 2008.Google Scholar