Experimental research on shear-slip characteristics of simulated fault with zigzag-type gouge

• A large number of micro-fractures generate reminiscently during shearing of zigzag gouge.
• Approaching to final failure, tangential force drop, AE and duration gradually reduce.
• Prior to zigzag failure, duration shows obvious steadiness verifying the “foreshock” effect.
• Influencing level of zigzag size on shear process and intensity is extremely significant.
• Normal force significantly affects duration among slips instead of shear intensity of zigzag.

We sheared layers of polymethyl methacrylate (PMMA) by traditional double-direct shear tests, and synchronously measured the acoustic emissions (AE) generated by shear-slip and friction. Laboratory observations of simulated fault by PMMA materials with zigzag-type gouge showing repetitive, shear-slip events that are reminiscent of earthquakes were verified. In addition, the influencing rules of zigzag size and normal force on shear-slip process and intensity, as well as AE were revealed. Especially, prior to final failure of zigzag, the duration among shear-slip events gradually decreases and shows significant steadiness, which may prove the probability of the obvious foreshock effect to a larger earthquake. Maybe, this work can interpret the shear-slip mechanism of earthquakes and even provide warnings of failure and instability of fault.