Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Earthquake Study by Scripps Scientists Produces New Depiction of Fault Zones


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:

More articles from Earth Sciences:

nachricht Oasis of life in the ice-covered central Arctic
24.10.2016 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Oasis of life in the ice-covered central Arctic

24.10.2016 | Earth Sciences

‘Farming’ bacteria to boost growth in the oceans

24.10.2016 | Life Sciences

Light-driven atomic rotations excite magnetic waves

24.10.2016 | Physics and Astronomy

More VideoLinks >>>