Microfracture processes in the breakdown zone during dynamic shear rupture inferred from laboratory observation of near-fault high-frequency strong motion

摘要: High-frequency velocities are measured during stick-slip motion in the immediate vicinity of a fault granite sample to reveal microscopic process taking place breakdown zone defined slip-weakening model. It is found that 1) onset time observed strong approximately coincides with local rupture time, 2) near-fault high-frequency strong-motion duration proportional and 3) power spectra motions exhibit significant amplitudes at frequencies above value offmax, wherefmax cut-off frequency relevant rupturing zone. These observations suggest would be due incoherent brittle microfracture whose characteristic scale much shorter than size. We present stochastic model synthesize velocity waveforms. In model, number small circular subfaults distributed randomly on an individual subfault assumed random. The main features waveforms well explained by this numerical modeling. concluded half total energy elastic waves point radiated from propagating emphasize importance observation for large shallow earthquakes.