DYNAMICAL WEAKENING OF FAULTS BY ACOUSTIC FLUIDIZATION

When a fault slips seismically, some of the energy released may excite strong, short-wavelength vibrations near the fault core. Such vibrati ons can temporarily reduce the normal stress on the fault, allowing it to slip at lower shear stresses than predicted by laboratory coeffici ents of friction. This phenomenon of 'acoustic fluidization' provides an alternative to theories that invoke pressurized fluids as an explan ation for why some faults appear to be so weak.