Nanoscale Roughness of Natural Fault Surfaces Controlled by Scale-Dependent Yield Strength Academic Article uri icon

abstract

  • ©2017. American Geophysical Union. All Rights Reserved. Many natural fault surfaces exhibit remarkably similar scale-dependent roughness, which may reflect the scale-dependent yield strength of rocks. Using atomic force microscopy (AFM), we show that a sample of the Corona Heights Fault exhibits isotropic surface roughness well-described by a power law, with a Hurst exponent of 0.75 +/− 0.05 at all wavelengths from 60 nm to 10 μm. The roughness data and a recently proposed theoretical framework predict that yield strength varies with length scale as λ-0.25+/−0.05. Nanoindentation tests on the Corona Heights sample and another fault sample whose topography was previously measured with AFM (the Yair Fault) reveal a scale-dependent yield stress with power-law exponents of −0.12 +/− 0.06 and −0.18 +/− 0.08, respectively. These values are within one to two standard deviations of the predicted value, and provide experimental evidence that fault roughness is controlled by intrinsic material properties, which produces a characteristic surface geometry.

author list (cited authors)

  • Thom, C. A., Brodsky, E. E., Carpick, R. W., Pharr, G. M., Oliver, W. C., & Goldsby, D. L.

publication date

  • January 1, 2017 11:11 AM