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Vadim K. Markov
Public Documents
2
COEXISTENCE OF FAST AND SLOW SLIP EVENTS IN LABORATORY SEISMIC CYCLES
Kseniya G. Morozova
and 4 more
August 21, 2020
The spectrum of slip modes on gouge-filled faults spans a continuum from fast ruptures to slow slip events. The nucleation of a certain slip mode is governed by the frictional heterogeneity of fault interface and the rheological fault stiffness. Though the pattern of mechanical parameter variation and dynamic stability loss during a seismic cycle is quite clear, it is important to have a unified seismic-acoustic signature of slow or fast slip event nucleation. We present laboratory acoustic emission (AE) experiments on a slider-model with a precise control of mechanical and AE parameters. A comprehensive analysis of AE activity points to the presence of two AE subpopulations. One of them manifests as pulses with harsh onsets. The second one exhibits a gradual amplitude rise and tremor-like signal. The second AE subpopulation shows a longer failure duration and increased energy dissipation. Regularities of changing the frequency-amplitude characteristics of AE subpopulations during a laboratory seismic cycle differ. The first AE subpopulation retains parameters of frequency-amplitude distribution, but the second one exhibits a pronounced cyclic recurrence of the b-value. The latter decreases before slip events and recovers after them. The detected features of AE subpopulations are common for the entire spectrum of slip modes. Findings reveal a coexistence of slow and fast modes at the same fault at the micro-scale and point to the unity of underlying physical mechanisms of different slip mode nucleation.
NUCLEATION OF FAST, INTERMEDIATE AND SLOW SLIP MODES ON THE SAME FAULT
Kseniya G. Morozova
and 4 more
November 19, 2020
The spectrum of slip modes on gouge-filled faults spans a continuum from fast ruptures to slow slip events. The nucleation of a certain slip mode is governed by the frictional heterogeneity of fault interface and the rheological fault stiffness. There is a mounting evidence that a single fault can host multiple slip modes. We present laboratory acoustic emission (AE) experiments on a slider-model. The entire spectrum of fault slip modes with a precise control of mechanical and AE parameters was reproduced and the unity of underlying mechanisms of slip mode nucleation was detected. A comprehensive analysis of AE activity allows revealing coexistence of two distinct subpopulations of acoustic pulses (APs) emitted during a seismic cycle and accompanying nucleation of different fault slip modes. One of them manifests as APs with harsh onsets. The second one exhibits a gradual amplitude rise and a tremor-like waveform. The second AP subpopulation shows longer failure duration and increased energy dissipation. During a seismic cycle, the first AP subpopulation retains parameters of frequency-amplitude distribution, while the second one exhibits a pronounced cyclic recurrence of the b-value. The b-value of the second subpopulation decreases before slip events and recovers after them. The detected features of AE evolution are common for the entire spectrum of fault slip modes.