Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Seismic monitors detect physical changes deep within faults


Nature publishes new findings that could lead to improved earthquake assessments

Seismologists have long known that the buildup of forces along fault zones cause the physical properties of rock and sediments to change deep inside the Earth, at the level where earthquakes occur. Based upon new findings, researchers believe they may be able to design active seismic monitoring systems that continually monitor these subtle changes, looking for telltale signs of an impending earthquake.

The new findings, published in the Dec. 4 issue of the journal Nature, are based on an extensive study of data collected between 1987 and 1997 by ultrasensitive borehole seismometers along the Parkfield segment of the San Andreas fault in central California. By comparing seismograms from a series of minor earthquakes that occurred both before and after a "slow" earthquake at Parkfield in 1993, the researchers were able to detect subtle changes in the level of stress along the fault zone that were caused by this event.

"Our study focused on S-waves, also known as shear waves, which are created during every earthquake," said study co-author Fenglin Niu, assistant professor of Earth Science at Rice University. "S-waves bounce off of deep fractures filled with fluid, and we believe our data show how these fluids were redistributed as a result of the aseismic event in 1993."

An aseismic event occurs when there is a significant amount of movement along a fault line. Unlike earthquakes, where movement occurs within a few seconds, aseismic movements can take place over days, weeks, months or even years. For this reason, they are sometimes called slow earthquakes.

Parkfield, a small town that lies on the San Andreas fault, was chosen as the site of a focused earthquake experiment by the U.S. Geological Survey because of the town’s history of magnitude-6 earthquakes. Such quakes occurred in 1857, 1881, 1901, 1922, 1934, and 1966. Believing that another magnitude-6 quake was likely to occur before 1993, the USGS began the Parkfield Experiment in 1985, positioning a dense network of instruments in an effort to capture unprecedented and detailed information about an earthquake as it happened. The long-expected magnitude-6 quake has yet to occur at Parkfield, though the annual probability remains around 10 percent.

For Niu and his colleagues, the dense network of instruments around Parkfield provided the critical data needed to prove that structural changes in faults can be detected with seismic instruments. Using data collected by borehole seismometers positioned about 200 meters below ground, the group looked at a series of areas that scattered the S-waves produced by minor quakes along the fault.

"With the seismic data from only one seismic station, it is very difficult to determine whether the physical properties of the material in the fault zone have changed or the positions of the minor earthquakes have shifted," said Niu.

Niu and colleagues Paul G. Silver of the Carnegie Institution in Washington, D.C., and Robert M. Nadeau and Thomas V. McEvilly, both of the University of California, Berkeley, were able to correct for movement errors by studying data from seismometers at various positions throughout the region.

Niu said the research could become increasingly important in coming years because it provides a basis for understanding the structural changes that could be viewed with active seismic monitoring systems. Given recent improvements in seismic technology, seismologists are now considering how to design active seismic systems that monitor fault behavior continuously.

The study was funded by Rice, the Carnegie Institution of Washington, NASA and the USGS.

Jade Boyd | EurekAlert!
Further information:

More articles from Earth Sciences:

nachricht Jacobs University supports new mapping of Mars, Mercury and the Moon
21.03.2018 | Jacobs University Bremen gGmbH

nachricht Thawing permafrost produces more methane than expected
20.03.2018 | GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

TRAPPIST-1 planets provide clues to the nature of habitable worlds

21.03.2018 | Physics and Astronomy

The search for dark matter widens

21.03.2018 | Materials Sciences

Natural enemies reduce pesticide use

21.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>