Featured Research

from universities, journals, and other organizations

Slow earthquakes may foretell larger events

Date:
August 15, 2013
Source:
Penn State
Summary:
Monitoring slow earthquakes may provide a basis for reliable prediction in areas where slow quakes trigger normal earthquakes, according to geoscientists.

Scanning electron microscope images showing localized shear surfaces in cross-section and oblique view. Sense of shear is top to the right Note striations on shear surface. Similar patterns appear with serpentine.
Credit: Haines, S. H.; Kaproth, B.; Marone, C.; Saffer, D. and B. A. van der Pluijm

Monitoring slow earthquakes may provide a basis for reliable prediction in areas where slow quakes trigger normal earthquakes, according to Penn State geoscientists.

Related Articles


"We currently don't have any way to remotely monitor when land faults are about to move," said Chris Marone, professor of geophysics. "This has the potential to change the game for earthquake monitoring and prediction, because if it is right and you can make the right predictions, it could be big."

Marone and Bryan Kaproth-Gerecht, recent Ph.D. graduate, looked at the mechanisms behind slow earthquakes and found that 60 seconds before slow stick slip began in their laboratory samples, a precursor signal appeared.

Normal stick slip earthquakes typically move at a rate of three to 33 feet per second, but slow earthquakes, while they still stick and slip for movement, move at rates of about 0.004 inches per second taking months or more to rupture. However, slow earthquakes often occur near traditional earthquake zones and may precipitate potentially devastating earthquakes.

"Understanding the physics of slow earthquakes and identifying possible precursory changes in fault zone properties are increasingly important goals," the researchers report on line in today's (Aug. 15) issue of Science Express.

Using serpentine, a common mineral often found in slow earthquake areas, Marone and Kaproth-Gerecht performed laboratory experiments applying shear stress to rock samples so that the samples exhibited slow stick slip movement. The researchers repeated experiments 50 or more times and found that, at least in the laboratory, slow fault zones undergo a transition from a state that supports slow velocity below about 0.0004 inches per second to one that essentially stops movement above that speed.

"We recognize that this is complicated and that velocity depends on the friction," said Marone. "We don't know for sure what is happening, but, from our lab experiments, we know that this phenomenon is occurring."

The researchers think that what makes this unusual pattern of movement is that friction contact strength goes down as velocity goes up, but only for a small velocity range. Once the speed increases enough, the friction contact area becomes saturated. It can't get any smaller and other physical properties take over, such as thermal effects. This mechanism limits the speed of slow earthquakes. Marone and Kaproth-Gerecht also looked at the primary elastic waves and the secondary shear waves produced by their experiments.

"Here we see elastic waves moving and we know what's going on with P and S waves and the acoustic speed," said Marone. "This is important because this is what you can see in the field, what seismographs record."

Marone notes that there are not currently sufficient measuring devices adjacent to known fault lines to make any type of prediction from the precursor signature of the movement of the elastic waves. It is, however, conceivable that with the proper instrumentation, a better picture of what happens before a fault moves in slip stick motion is possible and perhaps could lead to some type of prediction.


Story Source:

The above story is based on materials provided by Penn State. Note: Materials may be edited for content and length.


Journal Reference:

  1. Bryan M. Kaproth and C. Marone. Slow Earthquakes, Preseismic Velocity Changes, and the Origin of Slow Frictional Stick-Slip. Science, 15 August 2013 DOI: 10.1126/science.1239577

Cite This Page:

Penn State. "Slow earthquakes may foretell larger events." ScienceDaily. ScienceDaily, 15 August 2013. <www.sciencedaily.com/releases/2013/08/130815145148.htm>.
Penn State. (2013, August 15). Slow earthquakes may foretell larger events. ScienceDaily. Retrieved December 19, 2014 from www.sciencedaily.com/releases/2013/08/130815145148.htm
Penn State. "Slow earthquakes may foretell larger events." ScienceDaily. www.sciencedaily.com/releases/2013/08/130815145148.htm (accessed December 19, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Friday, December 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Lava on Track to Hit Hawaii Market

Raw: Lava on Track to Hit Hawaii Market

AP (Dec. 19, 2014) Lava from an active volcano on Hawaii's Big Island slowed slightly but stayed on track to hit a shopping center in the small town of Pahoa. (Dec. 19) Video provided by AP
Powered by NewsLook.com
Birds Might Be Better Meteorologists Than Us

Birds Might Be Better Meteorologists Than Us

Newsy (Dec. 19, 2014) A new study suggests a certain type of bird was able to sense a tornado outbreak that moved through the U.S. a day before it hit. Video provided by Newsy
Powered by NewsLook.com
Navy Unveils Robot Fish

Navy Unveils Robot Fish

Reuters - Light News Video Online (Dec. 18, 2014) The U.S. Navy unveils an underwater device that mimics the movement of a fish. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Arctic Warming Twice As Fast As Rest Of Planet

Arctic Warming Twice As Fast As Rest Of Planet

Newsy (Dec. 18, 2014) The Arctic is warming twice as fast as the rest of the planet, thanks in part to something called feedback. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins