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Dynamic Weakening by Acoustic Fluidization during Stick-Slip Motion.
F Giacco1,2, L Saggese3, L de Arcangelis3,4
1CNR-SPIN, Department of Physics, University of Naples "Federico II," Naples 80126, Italy.
Physical Review Letters
|October 3, 2015
Summary
Acoustic fluidization, driven by specific frequency waves, weakens faults and may trigger earthquakes. These acoustic waves naturally emerge during fault failure, validating their role in seismic events.
Area of Science:
- Geophysics
- Seismology
- Earthquake Science
Background:
- Faults can exhibit unexpected weakness, potentially due to acoustic fluidization.
- Acoustic fluidization is a proposed mechanism involving acoustic waves reducing confining pressure.
- This mechanism is also suggested to explain remote earthquake triggering.
Purpose of the Study:
- To numerically investigate and validate the acoustic fluidization mechanism in a granular fault model.
- To understand the role of acoustic waves in fault weakening and earthquake triggering.
Main Methods:
- Numerical simulation of a granular fault model.
- Analysis of stick-slip dynamics under perturbations.
- Investigation of acoustic wave emergence and frequency characteristics.
Main Results:
- Fault dynamics are sensitive to perturbations at a characteristic frequency of normal oscillations.
- Gradual dynamical weakening occurs as failure approaches.
- Acoustic waves at this characteristic frequency spontaneously emerge at failure onset.
Conclusions:
- The study validates acoustic fluidization as a mechanism for fault weakening.
- Spontaneously emerging acoustic waves support the relevance of this mechanism in earthquake triggering.
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