Synchronized oscillations and acoustic fluidization in confined granular materials

Area of Science:

• Geophysics
• Granular physics

Background:

• The acoustic fluidization hypothesis suggests internal elastic waves in seismic faults can cause failure.
• These waves generate normal stress, counteracting confining pressure.

Purpose of the Study:

• Investigate the mechanisms of acoustic fluidization wave activation in granular fault models.
• Examine particle behavior and stress dynamics preceding seismic fault failure.

Main Methods:

• Numerical simulations of a granular fault model.
• Analysis of particle trajectories and oscillations within the fault plane.

Main Results:

• Synchronized oscillations of backbone particles observed at the characteristic acoustic fluidization frequency.
• Oscillations reorient perpendicular to the fault plane under increasing shear stress, opposing confining pressure.
• External perturbations at the characteristic frequency can induce similar orientation changes.

Conclusions:

• Numerical simulations support the acoustic fluidization hypothesis.
• Particle oscillations play a key role in generating stress that leads to fault failure.
• The findings offer insights into seismic fault dynamics and failure mechanisms.