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 GPM sees deadly tornadic storms moving through US Southeast
01.12.2016 | NASA/Goddard Space Flight Center

nachricht Cyclic change within magma reservoirs significantly affects the explosivity of volcanic eruptions
30.11.2016 | Johannes Gutenberg-Universität Mainz

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>