Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Earthquake Study by Scripps Scientists Produces New Depiction of Fault Zones

13.09.2002


Analysis uncovers unusual earthquake-related deformation, paves the way for methods to identify new active faults


A geographic depiction of the Eastern California Shear Zone. The inset, displaying data from synthetic aperture radar interferometry (InSAR), shows the deformation induced by the 1999 Hector Mine earthquake on nearby faults.
© Scripps



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. ANIMATION


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.

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.

Mario Aguilera | alfa
Further information:
http://scrippsnews.ucsd.edu/pressreleases/fialko_science_faults.html

More articles from Earth Sciences:

nachricht By saving cost and energy, the lighting revolution may increase light pollution
23.11.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

nachricht Frictional Heat Powers Hydrothermal Activity on Enceladus
23.11.2017 | Universität Heidelberg

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Water cooling for the Earth's crust

23.11.2017 | Earth Sciences

Nano-watch has steady hands

23.11.2017 | Physics and Astronomy

Batteries with better performance and improved safety

23.11.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>