Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Los Angeles ’big squeeze’ continues, straining earthquake faults


Northern metropolitan Los Angeles is being squeezed at a rate of five millimeters [0.2 inches] a year, straining an area between two earthquake faults that serve as geologic bookends north and south of the affected region, according to NASA scientists.

The compression of the Los Angeles landscape is being monitored by a network of more than 250 precision global positioning system (GPS) receivers, known as the Southern California Integrated Global Positioning System Network (SCIGN), as well as by measurements from interferometric synthetic aperture radar (InSAR) satellites operated by the European Space Agency (ESA).

Information from these two sources of precision ground deformation measurements is accumulating and enhancing our knowledge of the forces shaping the land surface in the Los Angeles region. These forces include motions of the North American and Pacific tectonic plates and ground movement caused by human activities, such as oil drilling and pumping water into and out of local aquifers.

A team of scientists from NASA’s Jet Propulsion Laboratory and University of California at Los Angeles, led by Donald Argus, set out to distinguish between motions induced by human activity and those generated by movements of Earth’s tectonic plates. Their results, published in the Journal of Geophysical Research (Solid Earth) in April, indicate human-caused motions are very slow and could not account for the significant ground shift observed in northern Los Angeles.

The new study used space-based navigation to determine the exact position of hundreds of points around the metropolitan area to measure the strain building up across faults. Scientists expect that the strain will ultimately be released in earthquakes much like the 1994 Northridge temblor. The study also suggests which faults might be most likely to rupture. "These findings remove uncertainty about the rate at which strain is building up in northern metropolitan Los Angeles," Argus said. "In addition, by taking into account the effects of humans and observations from the many new global positioning system sites established in the past few years, we can identify the areas where strain is building the fastest."

He cautioned, however, that more studies are needed, since scientists do not yet fully understand the consequences and risks of this stress accumulation. "Nevertheless, these data have important implications for hazard management and retrofitting strategies," he said.

The study finds strain is rapidly accumulating within an area 12 to 25 kilometers [7.5 to 16 miles] south of the San Gabriel Mountains, primarily in the San Gabriel and San Fernando Valleys and nearby hills. The region is located between the Puente Hills fault, which begins south of downtown Los Angeles and extends east, and the Sierra Madre fault, which runs along the base of the San Gabriel Mountains

The new analysis indicates the crust above the Los Angeles segment of the Puente Hills Fault is being squeezed the most. The finding suggests that the Puente Hills Fault and nearby faults in the area, such as the upper Elysian Park Fault, may be more likely to break than those elsewhere in metropolitan Los Angeles. Previous studies have estimated the Puente Hills Fault might generate an earthquake of magnitude 6.6 to 7.5.

The researchers constructed models of the accumulating strain, varying which faults "creep" (move continuously without producing earthquakes), how fast they creep, and the depths at which the faults go from being "locked" in place (and building strain) to creeping. The model that best fit the actual global positioning system observations is one in which a thrust fault (a fault where one block of Earth shifts up or down relative to the other) is locked above six kilometers [four miles] deep and creeps at about nine millimeters [0.4 inches] a year beneath that depth. From that model, they inferred that the deep part of the Los Angeles segment of the Puente Hills Fault is creeping, as is a deep unknown buried fault east of downtown that lies north of the Whittier Fault and south of the Sierra Madre Fault. The model does not allow the researchers to determine which fault segments are locked.

Argus said a significant discrepancy exists between the relatively shallow locking depth of their model and the historical record of the depth of earthquakes that struck the region in 1971 and 1994, which were much deeper. Scientists speculate the discrepancy may be due to the presence of sediments filling parts of the Los Angeles basin. Further studies are planned to examine how these sediments may be affecting fault strain in the region.

The study used InSAR data collected from 1992 to 2000 from ESA’s European Remote Sensing satellite to estimate vertical ground motion. Horizontal strain buildup measurements were made from SCIGN observations from 1994 to 2004.

Harvey Leifert | EurekAlert!
Further information:

More articles from Earth Sciences:

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

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

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...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

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

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>