Laboratory experiments reproduce statistical behavior of earthquakes

Feb 21, 2013

Mechanical failure of materials is a complex phenomenon underlying many accidents and natural disasters ranging from the fracture of small devices to earthquakes. Despite the vast separation of spatial, temporal, energy, and strain-rate scales, and the differences in geometry, it has been proposed that laboratory experiments on brittle fracture in heterogeneous materials can be a model for earthquake occurrence.

A study led by researchers from the University of Barcelona, and published on the journal , has carried out experiments with a material loaded under compression that reproduces the four main statistical laws of seismicity: the Gutenberg-Ritcher law, the Omori's law, the distribution of waiting times between consecutive events and the productivity law.

The researcher Eduard Vives, from the Faculty of Physics of the UB, led the research in which collaborated several researchers from the Faculty —located at the BKC—, Xavier Illa, Antoni Planes and Jordi Baró (the main author), as well as Álvaro Corral, from the Centre for Mathematical Research (CERCA – Government of Catalonia), and researchers from the University of Cambridge, the University of Viena and the Institute for Scientific and Technological Research of San Luis Potosi (Mexico).

The material, analyzed by means of a device developed by the Materials Technological Unit of the Scientific and Technological Centers of the UB, is a porous glass (40 % porosity), designed for industrial applications, and named Vycor. The sample, about 5mm, was introduced between two plates and subjected to uniaxial compression that increases linearly until the sample fragments into pieces. were place on the compression plates. They will function as which measure ultrasonic and detect sample's fractures.

"The experiment carried out simulates the emergence of a new fault", explains the UB researcher Eduard Vives. "By this means —he continues—, we observed time distribution, which at the laboratory corresponds to some hours and in earthquakes to thousands of years". On the contrary, seismology study the space statistical changes considering the data obtained from high seismic activity areas, as California, and low activity ones. According to the researcher, "this symmetry in space and time reveals that it is probable that earthquakes behavior corresponds to any kind of self-organized criticality —as some theories state—, and if it could be proved, it would be a great advance to apply existent theories.

Several works have previously tried to establish comparisons between earthquakes and laboratory fracture of materials, mainly using rocks, but results were not completely reliable, as they do not reproduce all the properties of earthquakes. "This material allows to carried out experiments that control several parameters, such as or magnitude or speed", concludes Vives.

Four laws of statistical seismology

The results of the experiments performed with this material fulfill the four fundamental laws of statistical seismology. On the one hand, the energy detected by acoustic emissions varies as the Gutenberg-Ritcher law affirms; this law states that the number of earthquakes as a function of their radiated energy decreases as a power law.

To get a general idea of the different scales, it is important to remember that a big (magnitude 8) equals 1,000 Hiroshima bombs, whereas the maximum energy measured in the laboratory equals the fission energy of one uranium atom. This different magnitude corresponds, approximately, to a factor of 1027.

Another experiment made with this material studied the number of aftershocks produced after a big fracture and it has been observed that it decays with time, so the tendency to follow Omori's law is clear. "Laboratory maximum rate of aftershocks with time corresponds to some hours, whereas in earthquakes it last more than one hundred years", remarks the UB researcher.

The third law of statistical seismology is the one related to waiting times, which relates the time between two consecutive earthquakes. In this case, laboratory results obtained were compared to the ones got from the earthquakes happened in Southern California, and "although different scales, similarity is higher", affirms Vives. Finally, the productivity law was also proved, which relates the rate of aftershocks triggered by a mainshock to its magnitude: larger-magnitude earthquakes produce on average more aftershocks.

Explore further: New detector sniffs out origins of methane

More information: Baró, J. et al. Statistical similarity between the compression of a porous material and earthquakes, Physical Review Letters, 22nd February 2013. DOI: 10.1103/PhysRevLett.110.088702

add to favorites email to friend print save as pdf

Related Stories

Relationship between two recent New Zealand earthquakes

Sep 26, 2011

The relationship between two earthquakes that took place near Christchurch, New Zealand, in September 2010 and February 2011 is examined in a paper published in Scientific Reports. The findings suggest that t ...

Slow avalanches oscillate in new experiment

Oct 25, 2012

"Avalanches"—the crackling behavior of materials under slowly increasing stress, like crumpling paper or earthquakes—may have a novel facet previously unknown, say Cornell researchers.

Are we living in an age of giant quakes?

Apr 08, 2011

Searching for patterns in the occurrence of large magnitude earthquakes after a succession of large tremors -- surpassed by the recent magnitude-9.0 quake in Japan -- has researchers wondering if the amount ...

Earthquakes actually aftershocks of 19th century quakes

Nov 04, 2009

( -- When small earthquakes shake the central U.S., citizens often fear the rumbles are signs a big earthquake is coming. Fortunately, new research instead shows that most of these earthquakes ...

Recommended for you

New detector sniffs out origins of methane

9 hours ago

Methane is a potent greenhouse gas, second only to carbon dioxide in its capacity to trap heat in Earth's atmosphere for a long time. The gas can originate from lakes and swamps, natural-gas pipelines, deep-sea ...

The tides they are a changin'

13 hours ago

Scientists from the University of Southampton have found that ocean tides have changed significantly over the last century at many coastal locations around the world.

Lightning plus volcanic ash make glass

Mar 03, 2015

In their open-access paper for Geology, Kimberly Genareau and colleagues propose, for the first time, a mechanism for the generation of glass spherules in geologic deposits through the occurrence of volcan ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.