Effects of heterogeneous gouge segments on the slip behavior of experimental faults at dm scale

Frictional heterogeneity within fault zones is one of the factors proposed to explain spectrum slow, intermediate, and fast slip behaviors exhibited by faults in nature. Numerical modeling shows how even a simplified model setup incorporating sliding on velocity-weakening (VW) patch surrounded velocity-strengthening (VS) material can reproduce rich variety resembling However, experimental investigations heterogeneous are few. In this study, behavior three, 347 mm long × 50 wide, faults, constructed using diagonally sawcut PMMA forcing blocks, was investigated at low normal stresses (<10.5 MPa) room temperature. Fault friction controlled including an 80 long, 2 thick, central segment VW gypsum “gouge” flanked two VS segments composed calcite, quartz, or kaolinite. The length same order just below critical nucleation for gouge. Strain gauges multi-rate digital imaging were used map stress displacement along zone. At highest data showed confined ruptures, whereby rupture nucleated arrested strongly decelerated segments. Slip rates close dynamic rates, but significant slow also observed between rapid events. Lowering fault, from 10.5 1 MPa resulted events occurring uniformly over whole (calcite–gypsum fault), near-stable (quartz–gypsum persistent stick-slip as higher (kaolinite–gypsum fault). consistent with that predicted previous numerical frictionally similar geometry experiment. experiments concentrations influence behavior. Specifically, concentrations, formed due compaction kaolinite gouges, promoted unstable latter. Shear extremities caused occur segments, quartz–gypsum experiment seemed promote local stresses. thus gouge distribution, models theory applied both natural induced seismicity.