Crackling noise in cereal and magnets aids study of earthquakes

June 03, 2001

CHAMPAIGN, Ill. -- When Karin Dahmen hears the crackling noise in a bowl of crisped-rice cereal, her thoughts turn to earthquakes.

That's because both the cereal and an earthquake fault zone have something in common: Each responds to an external force with a power law distribution of events of all sizes, independent of microscopic or macroscopic details. By studying such universal behavior, which depends upon just a few basic properties, scientists may better understand the physics of earthquakes.

Dahmen, a physicist at the University of Illinois, initially studied a similar effect - called Barkhausen noise - in magnets. That work was done in collaboration with her thesis adviser, Jim Sethna at Cornell University. "Magnetic materials respond to an external field by changing their magnetization in a series of bursts, or avalanches," she said. "In highly disordered materials, we find small avalanches. But in clean materials, we find huge avalanches that sweep through the material." What all three systems - a bowl of cereal, a reel of magnetic tape and a fault zone - have in common is a competition between interaction and disorder, Dahmen said. "First, there is a slow driving force - such as a magnetic field in magnets or continental drift in earthquakes - and some interaction that promotes the avalanche. Then, there is some disorder that stops the avalanche. This competition between interaction and disorder creates a very broad distribution of avalanche sizes."

Dahmen and her colleagues - Daniel Fisher at Harvard University, Yehuda Ben-Zion at the University of Southern California, Deniz Ertas at Exxon Research and Engineering, and Sharad Ramanathan at Bell Labs - recently took the tools used to study noise in magnets and applied them to earthquake models. The tools, such as mean-field theory and renormalization group techniques, allowed the researchers to examine the interplay between disorder and dynamical effects in earthquakes.

Fault zones with highly irregular geometry display power law statistics over the entire range of observed magnitudes, Dahmen said. Faults with more regular geometry, however, display such distributions only for small events, which typically occur between much larger events that rupture a large fraction of the fault.

"Our model suggests a competition between the earthquake-promoting effect of seismic waves and the earthquake-stopping effect of heterogeneities in the fault plane," said Dahmen, who was to present the team's findings at the American Geophysical Union Spring Meeting May 29-June 2 in Boston. "In highly heterogeneous faults, dynamical effects can be neglected, and we expect to see the pure power law distribution. But in highly regular faults, the weakening effects of seismic waves become important." Earthquakes that grow larger than a critical size - which depends on the amount of disorder in the fault plane - become unstoppable in the presence of seismic waves, Dahmen said. "These earthquakes then grow to the characteristic runaway event size, in which a large fraction of the fault zone ruptures." -jk-
-end-


University of Illinois at Urbana-Champaign

Related Earthquakes Articles from Brightsurf:

AI detects hidden earthquakes
Tiny movements in Earth's outermost layer may provide a Rosetta Stone for deciphering the physics and warning signs of big quakes.

Undersea earthquakes shake up climate science
Sound generated by seismic events on the seabed can be used to determine the temperature of Earth's warming oceans.

New discovery could highlight areas where earthquakes are less likely to occur
Scientists from Cardiff University have discovered specific conditions that occur along the ocean floor where two tectonic plates are more likely to slowly creep past one another as opposed to drastically slipping and creating catastrophic earthquakes.

Does accelerated subduction precede great earthquakes?
A strange reversal of ground motion preceded two of the largest earthquakes in history.

Scientists get first look at cause of 'slow motion' earthquakes
An international team of scientists has for the first time identified the conditions deep below the Earth's surface that lead to the triggering of so-called 'slow motion' earthquakes.

Separations between earthquakes reveal clear patterns
So far, few studies have explored how the similarity between inter-earthquake times and distances is related to their separation from initial events.

How earthquakes deform gravity
Researchers at the German Research Centre for Geosciences GFZ in Potsdam have developed an algorithm that for the first time can describe a gravitational signal caused by earthquakes with high accuracy.

Bridge protection in catastrophic earthquakes
Bridges are the most vulnerable parts of a transport network when earthquakes occur, obstructing emergency response, search and rescue missions and aid delivery, increasing potential fatalities.

Earthquakes, chickens, and bugs, oh my!
Computer scientists at the University of California, Riverside have developed two algorithms that will improve earthquake monitoring and help farmers protect their crops from dangerous insects, or monitor the health of chickens and other animals.

Can a UNICORN outrun earthquakes?
A University of Tokyo Team transformed its UNICORN computing code into an AI-like algorithm to more quickly simulate tectonic plate deformation due to a phenomenon called a ''fault slip,'' a sudden shift that occurs at the plate boundary.

Read More: Earthquakes News and Earthquakes Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.