Laboratory modeling of displacements of rock blocks: Low-amplitude fast movements in experiments on a slider model of fault
DOI:
https://doi.org/10.21638/spbu07.2024.201Abstract
Experimental modeling of physical processes associated with faults of the Earth's crust is important for studying earthquakes, rock burst and processes accompanying the deposit development. Laboratory experiments with the study of stick-slip sliding of rock blocks relative to each other on a fault slider model have become widespread. Stick-slip sliding manifests itself in the form of episodes of rapid displacement when load increases to a critical value. The paper investigated the reaction of the model under conditions of different fault humidity after increasing load to a subcritical value. After five days of fault wetting and three series of loads, small and fast displacements (microstick-slips) were detected by signals of a three-component high-frequency accelerometer. Microstick-slips are two orders of magnitude smaller than displacements during episodes of the traditionally observed stick-slip. After time has elapsed since the loading stopped, intervals between microstick-slips increase faster than according to the power law. Magnitude of displacement, amplitude of accelerations and pulses of acoustic emission gradually decreases with reaching the plateau. Possible qualitative mechanisms of the occurrence of microstick-slips are proposed, taking into account the gradual wetting and drying of the fault zone after water injection. The main hypothesis is competition of hardening and softening processes in the fault zone during the removal of water from the fault due to drying and action of capillary forces. Uneven propagation of these processes along the fault can create prerequisites for either small linear displacement on a limited section of the fault, or small displacement with rotation. These displacements manifest themselves as microstick-slips. General slow slippage along the fault and decrease in shear stress leads to decrease in frequency of microstick-slips and in their characteristic parameters.
Keywords:
laboratory modeling, earthquakes, fault, fluid injection, acceleration, stick-slip
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