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 Less radiation in inner Van Allen belt than previously believed
21.03.2017 | DOE/Los Alamos National Laboratory

nachricht Mars volcano, Earth's dinosaurs went extinct about the same time
21.03.2017 | NASA/Goddard Space Flight Center

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Pulverizing electronic waste is green, clean -- and cold

22.03.2017 | Materials Sciences

Astronomers hazard a ride in a 'drifting carousel' to understand pulsating stars

22.03.2017 | Physics and Astronomy

New gel-like coating beefs up the performance of lithium-sulfur batteries

22.03.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>