Experimental constraints on energy partitioning during stick-slip and stable sliding within analog fault gouge

Abstract : The lack of substantial frictional heat anomalies across major fault zones has been a key observation suggesting that faults support low shear stress during slip. Some studies have suggested that the lack of large thermal anomalies across faults may be a result of considerably less energy going to frictional heat than generally thought and that a large fraction of energy is dissipated by other processes such as the creation of new surface area. We evaluate this hypothesis through the analysis of laboratory shear experiments for both stick-slip (seismic) and stably sliding (aseismic) analog fault gouges. These experiments differ from previous laboratory studies in that they 1) provide independent constraints on frictional heat generation and energy consumed generating new surface area, 2) cover a broader range of shear stresses (2-20 MPa) than most previous studies, and 3) evaluate both stick-slip and stable sliding within granular material. Based on the analysis of high-precision temperature measurements and comparisons with numerical model simulations > 90% of the total energy appears to go to frictional heat generation (EH) for all of our experiments. We also show based on grain size analysis that ~ 1% of total work is consumed generating new surface area (ESA). These results are consistent with assumptions allowing frictional resistance to be inferred from thermal data. Furthermore, we observe no resolvable difference in the fraction of energy going to fracturing or frictional heat between stick-slip and stable sliding experiments.