Aftershock sequences and seismic-like organization of acoustic events produced by a single propagating crack

TL;DR

This study reveals that acoustic emissions from a single propagating crack exhibit aftershock-like sequences and scale-free distributions, governed by crack speed, thus unifying fracture and seismic event organization.

Contribution

It demonstrates that seismic-like acoustic event organization occurs even in simple crack propagation, linking statistical laws to crack dynamics and scale-free distributions.

Findings

Acoustic events follow aftershock sequences similar to earthquakes.

Event energy and timing distributions are scale-free.

Crack speed influences the organization of acoustic emissions.

Abstract

Brittle fractures of inhomogeneous materials like rocks, concrete, or ceramics are of two types: Nominally brittle and driven by the propagation of a single dominant crack or quasi-brittle and resulting from the accumulation of many microcracks. The latter goes along with acoustic noise, whose analysis has revealed that events form aftershock sequences obeying characteristic laws reminiscent of those in seismology. Yet, their origin lacks explanation. Here we show that such a statistical organization is not only specific to the multi-cracking situations of quasi-brittle failure and seismology, but also rules the acoustic events produced by a propagating crack. This simpler situation has permitted us to relate these laws to the overall scale-free distribution of inter-event time and energy and to uncover their selection by the crack speed. These results provide a comprehensive picture of how acoustic events are organized upon material failure in the most fundamental of fracture states: single propagating cracks.