Nanoscale Roughness of Natural Fault Surfaces Controlled by Scale-Dependent Yield Strength
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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 60nm to 10m. The roughness data and a recently proposed theoretical framework predict that yield strength varies with length scale as -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.
Geophysical Research Letters
author list (cited authors)
Thom, C. A., Brodsky, E. E., Carpick, R. W., Pharr, G. M., Oliver, W. C., & Goldsby, D. L.
complete list of authors
Thom, CA||Brodsky, EE||Carpick, RW||Pharr, GM||Oliver, WC||Goldsby, DL