Analogies Between the Cracking Noise of Ethanol-Dampened Charcoal and Earthquakes

Abstract

We report on an extensive characterization of the cracking noise produced by charcoal samples when dampened with ethanol. We argue that the evaporation of ethanol causes transient and irregularly distributed internal stresses that promote the fragmentation of the samples and mimic some situations found in mining processes. The results show that, in general, the most fundamental seismic laws ruling earthquakes (the Gutenberg-Richter law, the unified scaling law for the recurrence times, Omori's law, the productivity law, and Båth's law) hold under the conditions of the experiment. Some discrepancies were also identified (a smaller exponent in the Gutenberg-Richter law, a stationary behavior in the aftershock rates for long times, and a double power-law relationship in the productivity law) and are related to the different loading conditions. Our results thus corroborate and elucidate the parallel between the seismic laws and fracture experiments caused by a more complex loading condition that also occurs in natural and induced seismicity (such as long-term fluid injection and gas-rock outbursts in mining processes).

Triggering Processes in Rock Fracture

“…[25,26] both provide clear examples that spatial localization and an increase in activity rates do not necessarily imply triggering behavior associated with aftershocks. Another uniaxial compression experiment seems to suggest time-dependent deviations from the OU relation [27], while other studies suggest that the OU relation is a general or even universal signature of relaxation processes in rock fracture independent of the specific perturbation source [8,28].…”

Extensive characterization of seismic laws in acoustic emissions of crumpled plastic sheets

“…The functional form of P (τ ) is usually approximated by a power law when r is time dependent, and by a gamma distribution when r is nearly stationary. For instance, P (τ ) was found to follow power laws for the cracking noise of a porous material under compression [23], whereas a gamma distribution describes the recurrence times between acoustic events in charcoal samples under irregularly distributed internal stresses [27]. In paper peeling experiments [36], an analysis of the recurrence time distribution with E min = 0 found an approximate power-law regime that is dependent on the driving forces.…”

“…We still lack a complete parallel (such as those reported in Refs. [23,27] for material fractures) with the other four fundamental seismic laws previously mentioned. Here we fill this hiatus by presenting an extensive parallel between the acoustic emissions of plastic sheets and earthquakes laws.…”

“…Our next step has been to define the mainshock events and the sequence of aftershocks for studying the Omori's law. Similarly to other acoustic experiments on material fractures [23,27], we consider as mainshocks all events with energy E ms in the range [10 j , 10 j+1 ] (with j = −8.75, −8.50, −8.25, . .…”

“…In addition to being observed for earthquakes, some of these laws have been individually reported in very diverse contexts, and particularly in the context of fractures of materials [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], where they find a broad range of applications in engineering and also serve as laboratory experiments for modeling earthquakes. All these phenomena have the common feature of producing impulsive and discrete events (crackling noises) of extremely varied sizes [29].…”