Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Earthquake 'memory' could spur aftershocks

07.01.2008
Experiment indicates sound waves can trigger quakes

Using a novel device that simulates earthquakes in a laboratory setting, a Los Alamos researcher and his colleagues have shown that seismic waves—the sounds radiated from earthquakes—can induce earthquake aftershocks, often long after a quake has subsided.

The research provides insight into how earthquakes may be triggered and how they recur.

In a letter appearing today in Nature, Los Alamos researcher Paul Johnson and colleagues Heather Savage, Mike Knuth, Joan Gomberg, and Chris Marone show how wave energy can be stored in certain types of granular materials—like the type found along certain fault lines across the globe—and how this stored energy can suddenly be released as an earthquake when hit by relatively small seismic waves far beyond the traditional “aftershock zone” of a main quake.

Perhaps most surprising, researchers have found that the release of energy can occur minutes, hours, or even days after the sound waves pass; the cause of the delay remains a tantalizing mystery.

Earthquakes happen when the Earth’s crust slips along cracks, known as faults. Major faults can be found at the junction of independently moving masses of crust and mantle, known as tectonic plates.

Each earthquake releases seismic waves—vibrations at the cusp, or below the range of human hearing—that travel through the Earth. These waves can trigger aftershocks in a zone several to tens of miles away from the radiating main earthquake, known as a “mainshock.” Most aftershocks usually occur within hours to days after the mainshock.

Researchers often have assumed that seismic waves beyond the immediate aftershock zone were too weak to trigger aftershocks. However, Gomberg and others have proven that seismic activity sometimes increases at least thousands of miles away after an earthquake.

“At these farther distances, earthquake triggering doesn’t happen all the time,” said Johnson. “The question always was why? What was going on in certain regions that lead to triggering? The challenge was whether we could go into the laboratory and mimic the conditions that go on inside the Earth and find out.”

The answer to the challenge lay at Pennsylvania State University, where Marone had developed an apparatus that mimics earthquakes by pressing plates atop a layer of tiny glass beads. When enough energy is applied to the plates, they slip, like tectonic plates above the mantle.

Johnson wondered whether sound waves could induce earthquakes in such a system. His colleagues originally believed sound would have no effect.

Much to their surprise, the earthquake machine revealed that when sound waves were applied for a short period just before the quake, they could induce smaller quakes, or, in some instances, delay the occurrence of the next major one. The sound waves seemed to affect earthquake behavior for as many as 10 earthquake events after they were applied.

More surprising still, the team found that the granular beads could store a “memory” even after the system had undergone a quake and the beads had rearranged themselves.

“The memory part is the most puzzling,” Johnson said, “because during an earthquake there is so much energy being released and the event is so violent that you have to wonder, why doesn’t the system reset itself?”

The research has helped confirm that earthquakes are periodic events and that sound can disrupt them.

But catastrophic events in other granular media—such as avalanches or the sudden collapse of sand dunes—could help provide clues into the physics of earthquakes, and could help Johnson and his colleagues begin to unravel the mystery of stored memory in granular systems.

“What we’ve created in the laboratory has provided the basis for an understanding of dynamic triggering of earthquakes, something that has mystified people for years,” said Johnson.

James E. Rickman | EurekAlert!
Further information:
http://www.lanl.gov

More articles from Earth Sciences:

nachricht A damming trend
17.12.2018 | Michigan State University

nachricht Live from the ocean research vessel Atlantis
13.12.2018 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Data storage using individual molecules

Researchers from the University of Basel have reported a new method that allows the physical state of just a few atoms or molecules within a network to be controlled. It is based on the spontaneous self-organization of molecules into extensive networks with pores about one nanometer in size. In the journal ‘small’, the physicists reported on their investigations, which could be of particular importance for the development of new storage devices.

Around the world, researchers are attempting to shrink data storage devices to achieve as large a storage capacity in as small a space as possible. In almost...

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Formed to Meet Customers’ Needs – New Laser Beams for Glass Processing

17.12.2018 | Physics and Astronomy

Preserving soil quality in the long term

17.12.2018 | Architecture and Construction

New RNA sequencing strategy provides insight into microbiomes

17.12.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>