Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Earthquakes beget earthquakes near and far

01.06.2004


Earthquakes not only shake up the local area but they also increase the rate of earthquake events locally and at a distance. The answer to how this happens may be in the laboratory, according to a Penn State researcher.



"We have learned a lot since the Landers earthquake in the Mojave Desert in 1992," says Dr. Chris Marone, professor of geosciences. "We learned that earthquake triggering happens a lot more than we thought. The mechanism is not well understood."

Marone is working with Margaret S. Boettcher, a Ph.D. student he coadvises at the Massachusetts Institute of Technology, and Heather M. Savage, his Ph.D student at Penn State, investigating in the laboratory the way triggering of earthquakes works and whether or not a time lag exists between the initial earthquake and the ones that follow.


The researchers use a deformation apparatus that simulates the fault zone between slipping rock masses and the slipping forces on it. Then a force is placed perpendicular to the fault to simulate the perpendicular vibration caused by the energy waves from the initial earthquake on the already stressed "fault." The researchers reported their results in a recent issue of the Journal of Geophysical Research.

"Yes, we do find lags between the changes in the forces and the changes in the strength," says Marone. "There are seconds of delay in the laboratory between the force being applied and the fault moving."

While the delay in the laboratory is in seconds, in the real world the delay can be from minutes to a week after the initial shock. The researchers believe they know why a delay exists between the vibration waves of the initial earthquake and the motion on other faults. The area of interest is the gouge zone, the space between the solid rock filled with everything from sand to pea size gravel to large boulders. This granular fault gouge can be up to a kilometer in width.

"We have known since the 1800s that compacted grains when sheared expand and increase volume," says Marone. "The best example of this phenomenon, known as dilatancy, is on the beach. Your foot, as you step, shears the compacted sand and the beach surface dries momentarily as water drains into the pore space between grains. When you lift your foot, the granules collapse back into their compacted position, leaving a dry footprint."

Within this gouge zone, a competition between compaction and dilation of the granules takes place. The perpendicular force of the periodic waves produced by the initial earthquake changes the steady state density and porosity. The change in porosity is dilation. Through compaction and dilation, an area parallel to the fault in the gouge is set up where the slipping movement of the earthquake actually takes place.

The Lander’s earthquake was a shallow earthquake and created many surface waves. Other similar earthquakes have occurred in the Mojave, Denali, the Hector Mine earthquake and in ChiChi, Taiwan. Potential for this type of earthquakes exists worldwide.

"People have been taking laboratory data and trying to model seismic hazard from trigger earthquakes," says Marone. "The lag between the time stresses reaches a fault and, when the strength in the fault gouge changes, must be considered to model this properly." The National Science Foundation and the United States Geological Service funded this research.

A’ndrea Elyse Messer | EurekAlert!
Further information:
http://www.psu.edu/

More articles from Earth Sciences:

nachricht A promising target in the quest for a 1-million-year-old Antarctic ice core
24.05.2018 | University of Washington

nachricht Tropical Peat Swamps: Restoration of Endangered Carbon Reservoirs
24.05.2018 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>