Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A New Level of Earthquake Understanding

06.03.2015

Surprise Findings from Berkeley Lab X-ray Study of San Andreas Fault Rock Sample

As everyone who lives in the San Francisco Bay Area knows, the Earth moves under our feet. But what about the stresses that cause earthquakes? How much is known about them? Until now, our understanding of these stresses has been based on macroscopic approximations. Now, the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) is reporting the successful study of stress fields along the San Andreas fault at the microscopic scale, the scale at which earthquake-triggering stresses originate.


U.S. Geological Survey

The notorious San Andreas Fault runs virtually the entire length of California

Working with a powerful microfocused X-ray beam at Berkeley Lab’s Advanced Light Source (ALS), a DOE Office of Science User Facility, researchers applied Laue X-ray microdiffraction, a technique commonly used to map stresses in electronic chips and other microscopic materials, to study a rock sample extracted from the San Andreas Fault Observatory at Depth (SAFOD). The results could one day lead to a better understanding of earthquake events.

“Stresses released during an earthquake are related to the strength of rocks and thus in turn to the rupture mechanism,” says Martin Kunz, a beamline scientist with the ALS’s Experimental Systems Group. “We found that the distribution of stresses in our sample were very heterogeneous at the micron scale and much higher than what has been reported with macroscopic approximations. This suggests there are different processes at work at the microscopic and macroscopic scales.”

Kunz is one of the co-authors of a paper describing this research in the journal Geology. The paper is titled “Residual stress preserved in quartz from the San Andreas Fault Observatory at Depth.” Co-authors are Kai Chen, Nobumichi Tamura and Hans-Rudolf Wenk.

Most earthquakes occur when stress that builds up in rocks along active faults, such as the San Andreas, is suddenly released, sending out seismic waves that make the ground shake. The pent- up stress results from the friction caused by tectonic forces that push two plates of rock against one another.

“In an effort to better understand earthquake mechanisms, several deep drilling projects have been undertaken to retrieve material from seismically active zones of major faults such as SAFOD,” says co-author Wenk, a geology professor with the University of California (UC) Berkeley’s Department of Earth and Planetary Science and the leading scientist of this study. “These drill-core samples can be studied in the laboratory for direct information about physical and chemical processes that occur at depth within a seismically active zone. The data can then be compared with information about seismicity to advance our understanding of the mechanisms of brittle failure in the Earth’s crust from microscopic to macroscopic scales.”

Kunz, Wenk and their colleagues measured remnant or “fossilized” stress fields in fractured quartz crystals from a sample taken out of a borehole in the San Andreas Fault near Parkfield, California at a depth of 2.7 kilometers. The measurements were made using X-ray Laue microdiffraction, a technique that can determine elastic deformation with a high degree of accuracy. Since minerals get deformed by the tectonic forces that act on them during earthquakes, measuring elastic deformation reveals how much stress acted on the minerals during the quake.

“Laue microdiffraction has been around for quite some time and has been exploited by the materials science community to quantify elastic and plastic deformation in metals and ceramics, but has been so far only scarcely applied to geological samples”, says co-author Tamura, a staff scientist with the ALS’s Experimental Systems Group who spearheads the Laue diffraction program at the ALS.

The measurements were obtained at ALS beamline 12.3.2, a hard (high-energy) X-ray diffraction beamline specialized for Laue X-ray microdiffraction.

“ALS Beamline 12.3.2 is one of just a few synchrotron-based X-ray beamlines in the world that can be used to measure residual stresses using Laue micro diffraction,” Tamura says.

In their analysis, the Berkeley researchers found that while some of the areas within individual quartz fragments showed no elastic deformation, others were subjected to stresses in excess of 200 million pascals (about 30,000 psi). This is much higher than the tens of millions of pascals of stress reported in previous indirect strength measurements of SAFOD rocks.

“Although there are a variety of possible origins of the measured stresses, we think these measured stresses are records of seismic events shocking the rock”, says co-author Chen of China’s Xi’an Jiantong University. It is the only mechanism consistent with the geological setting and microscopic observations of the rock.”

The authors believe their Laue X-ray microdiffraction technique has great potential for measuring the magnitude and orientation of residual stresses in rocks, and that with this technique quartz can serve as “paleo-piezometer” for a variety of geological settings and different rock types.

“Understanding the stress fields under which different types of rock fail will help us better understand what triggers earthquakes,” says Kunz. “Our study could mark the beginning of a whole new era of quantifying the forces that shape the Earth.”

This research was supported by the DOE Office of Science.

Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov 

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov/.

Contact Information
Lynn Yarris
Senior Writer, Media Coordinator
LCYarris@lbl.gov
Phone: 510-486-5375
Mobile: 510 717-9625

Lynn Yarris | newswise

Further reports about: X-ray earthquake earthquakes elastic elastic deformation materials microscopic quartz stresses

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 >>>