Constraints on the strength of the upper crust from stress inversion of fault slip data

The coefficient of friction of small faults in the field are estimated by stress inversion of fault slip data which incorporates the Coulomb failure criterion. The coefficients of friction determined for 27 fault clusters in limestone, sandstone, and basalt range from 0.0 to 1.3 with mean value of 0.58 ± 0.37. These values are in general agreement with the friction of 0.6-0.85 determined from laboratory experiments. The magnitudes of the calculated principal stresses are compared with in situ stress measurements in similar tectonic environments. -from Authors