Featured Research

from universities, journals, and other organizations

Earthquake Study By Scripps Scientists Produces New Depiction Of Fault Zones

Date:
September 13, 2002
Source:
Scripps Institution Of Oceanography
Summary:
On Oct. 16, 1999, approximately 37 miles from Palm Springs, Calif., a magnitude 7.1 earthquake ripped through 28 miles of faults in the Mojave Desert. Because of the area's sparse population and development, the massive quake caused virtually no major measurable injuries or destruction. Yet the "Hector Mine" event, named after a long-abandoned mine in the area, has produced a treasure of information about earthquakes, faults, and ruptures for scientists at Scripps Institution of Oceanography at the University of California, San Diego.

On Oct. 16, 1999, approximately 37 miles from Palm Springs, Calif., a magnitude 7.1 earthquake ripped through 28 miles of faults in the Mojave Desert. Because of the area's sparse population and development, the massive quake caused virtually no major measurable injuries or destruction. Yet the "Hector Mine" event, named after a long-abandoned mine in the area, has produced a treasure of information about earthquakes, faults, and ruptures for scientists at Scripps Institution of Oceanography at the University of California, San Diego. In results published in the Sept. 13 issue of Science, the scientists, along with a colleague at the California Institute of Technology (Caltech), reveal that they used satellite and radar technologies to uncover never-before documented characteristics of faults. These include the first evidence that faults move backwards, contrary to conventional observations, and indications that the material within faults is significantly different than its surroundings.

Related Articles


Scripps's Yuri Fialko, the lead author of the study, says the implications of the study include providing a new way to identify potentially active faults, helping to track when the last earthquake occurred in a fault zone, and perhaps better understanding the earthquake process.

Fialko calls the Hector Mine event the "perfect" earthquake for the satellite and radar technologies that he and his colleagues used. It is the first event comprehensively imaged using interferometric synthetic aperture radar (InSAR), as Fialko and coauthors demonstrated in an earlier study published in Geophysical Research Letters. InSAR uses a series of satellite recordings to detect changes in Earth's surface.

According to Science study coauthor David Sandwell, the fresh data gave researchers an uncommon and immediate window into earthquake processes in fault areas that are only typically imaged after being altered by natural forces such as rainstorms and unnatural forces such as off-road vehicle disruption.

Fialko, Sandwell, and coauthors Duncan Agnew, Peter Shearer, and Bernard Minster of Scripps, and Mark Simons of Caltech, studied the information to find unusual signatures of fault displacements caused by Hector Mine in the Eastern California Shear Zone (ECSZ) in an area thought to be relatively inactive.

The most surprising finding was the first evidence that faults can move backwards. Prior to an earthquake, faults are locked in position by the "glue" of friction. Changes due to energy released during earthquakes cause faults to move.

"Even small stress perturbations from distant earthquakes can cause faults to move a little bit, but it's only been known to cause this motion in a forward sense," said Fialko. "Here we observed the faults coming backwards due to relatively small stress changes, which is really quite unusual."

The study argues that the backward motion on the faults is caused by the dissimilar material within the faults, rather than the frictional failure.

"We used an analysis model that effectively says that material within the faults is mechanically distinct from the material surrounding the faults," said Fialko, of the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics at Scripps. "The rocks within the faults appear to be softer."

He says the fault zones become strained during periods of stress, acting like a soft, sponge-like material. The soft area thus becomes squeezed during periods of energy release.

According to Fialko, the results will guide new seismic studies to areas with contrasting fault material, such as that seen in the Eastern California Shear Zone. They can then be used as a way of identifying potentially active faults.

Another possibility emerges through studying the properties of fault zones over time.

"Measurements of changes in the mechanical properties of faults may yield valuable information about the earthquake cycle. For example, we might be able to say how long it was before the fault experienced an earthquake and how long it takes to heal," said Fialko.

Coauthor Shearer attributes these detailed results to the "breakthrough" offered by InSAR technology.

"Prior to InSAR, all we had were spot measurements of the deformation field," said Shearer. "At best we had maybe a few hundred points across southern California. You had a point here and there so you didn't really know what was happening. With InSAR we have millions of points and thus a continuous picture of deformation across southern California."

The scientists say the findings became possible due to highly successful satellite missions of the European Space Agency.

"We hope that NASA will launch the U.S. InSAR satellites to monitor surface changes in California and elsewhere," Fialko said. "This will dramatically improve our ability to study earthquakes as well as other potentially hazardous phenomena, such as volcanic activity and man-made deformation."

The research was supported by the Southern California Earthquake Center and the National Science Foundation (NSF). Synthetic aperture radar data were purchased with funding from NASA, the U.S. Geological Survey, and NSF.


Story Source:

The above story is based on materials provided by Scripps Institution Of Oceanography. Note: Materials may be edited for content and length.


Cite This Page:

Scripps Institution Of Oceanography. "Earthquake Study By Scripps Scientists Produces New Depiction Of Fault Zones." ScienceDaily. ScienceDaily, 13 September 2002. <www.sciencedaily.com/releases/2002/09/020913064356.htm>.
Scripps Institution Of Oceanography. (2002, September 13). Earthquake Study By Scripps Scientists Produces New Depiction Of Fault Zones. ScienceDaily. Retrieved October 31, 2014 from www.sciencedaily.com/releases/2002/09/020913064356.htm
Scripps Institution Of Oceanography. "Earthquake Study By Scripps Scientists Produces New Depiction Of Fault Zones." ScienceDaily. www.sciencedaily.com/releases/2002/09/020913064356.htm (accessed October 31, 2014).

Share This



More Earth & Climate News

Friday, October 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

How A Chorus Led Scientists To A New Frog Species

How A Chorus Led Scientists To A New Frog Species

Newsy (Oct. 30, 2014) A frog noticed by a conservationist on New York's Staten Island has been confirmed as a new species after extensive study and genetic testing. Video provided by Newsy
Powered by NewsLook.com
Raw: Hawaii Lava Approaching Village Road

Raw: Hawaii Lava Approaching Village Road

AP (Oct. 30, 2014) The lava flow on the Big Island of Hawaii was 225 yards from Pahoa Village Road on Wednesday night. The lava is slowing down but still approaching the village. (Oct. 30) Video provided by AP
Powered by NewsLook.com
Endangered Carpathian Ponies Are Making a Comeback in Poland

Endangered Carpathian Ponies Are Making a Comeback in Poland

AFP (Oct. 29, 2014) At the foot of the rugged Carpathian mountains near the Polish-Ukrainian border, ranchers and scientists are trying to protect the Carpathian pony, known as the Hucul in Polish. Duration: 02:17 Video provided by AFP
Powered by NewsLook.com
Deadly Mudslide in Sri Lanka Buries Houses

Deadly Mudslide in Sri Lanka Buries Houses

AP (Oct. 29, 2014) A mudslide triggered by monsoon rains buried scores of workers' houses at a tea plantation in central Sri Lanka on Wednesday, killing at least 10 people and leaving more than 250 missing, an official said. (Oct. 29) Video provided by AP
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