James Byerlee synthesized laboratory measurements of rock friction, providing the empirical basis of Byerlee's law. The work compares the shear stress needed for sliding with the normal compressive stress and examines effects of roughness and fault gouge.[ref]
Friction of rocks by James Byerlee. Abstract and Conclusions: normal-stress regimes, roughness and low-friction gouge exceptions
The experiments explain why many rocks show similar sliding resistance at high normal stress while some gouge-rich faults can be much weaker. Applying the laboratory relation to a natural fault also requires its fluid-pressure and material conditions.
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