Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Earthquakes beget earthquakes near and far


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:

More articles from Earth Sciences:

nachricht UCI and NASA document accelerated glacier melting in West Antarctica
26.10.2016 | University of California - Irvine

nachricht Ice shelf vibrations cause unusual waves in Antarctic atmosphere
25.10.2016 | American Geophysical Union

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 light sources made of 2D materials

Physicists from the University of Würzburg have designed a light source that emits photon pairs. Two-photon sources are particularly well suited for tap-proof data encryption. The experiment's key ingredients: a semiconductor crystal and some sticky tape.

So-called monolayers are at the heart of the research activities. These "super materials" (as the prestigious science magazine "Nature" puts it) have been...

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

All Focus news of the innovation-report >>>



Event News

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

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Prototype device for measuring graphene-based electromagnetic radiation created

28.10.2016 | Power and Electrical Engineering

Gamma ray camera offers new view on ultra-high energy electrons in plasma

28.10.2016 | Physics and Astronomy

When fat cells change their colour

28.10.2016 | Life Sciences

More VideoLinks >>>