Effects of acoustic waves on stick-slip in granular media and implications for earthquakes

Paul A. Johnson, Heather Savage, Matt Knuth, Joan Gomberg, Chris Marone

Research output: Contribution to journalArticlepeer-review

150 Scopus citations

Abstract

It remains unknown how the small strains induced by seismic waves can trigger earthquakes at large distances, in some cases thousands of kilometres from the triggering earthquake, with failure often occurring long after the waves have passed. Earthquake nucleation is usually observed to take place at depths of 10-20 km, and so static overburden should be large enough to inhibit triggering by seismic-wave stress perturbations. To understand the physics of dynamic triggering better, as well as the influence of dynamic stressing on earthquake recurrence, we have conducted laboratory studies of stick-slip in granular media with and without applied acoustic vibration. Glass beads were used to simulate granular fault zone material, sheared under constant normal stress, and subject to transient or continuous perturbation by acoustic waves. Here we show that small-magnitude failure events, corresponding to triggered aftershocks, occur when applied sound-wave amplitudes exceed several microstrain. These events are frequently delayed or occur as part of a cascade of small events. Vibrations also cause large slip events to be disrupted in time relative to those without wave perturbation. The effects are observed for many large-event cycles after vibrations cease, indicating a strain memory in the granular material. Dynamic stressing of tectonic faults may play a similar role in determining the complexity of earthquake recurrence.

Original languageEnglish (US)
Pages (from-to)57-60
Number of pages4
JournalNature
Volume451
Issue number7174
DOIs
StatePublished - Jan 3 2008

All Science Journal Classification (ASJC) codes

  • General

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