Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

San Jacinto fault is younger than thought, rises in seismic importance

25.10.2006
Slip rate of southern California fault may be faster than previously believed

A detailed study of sedimentary rocks exposed along a portion of southern California's San Jacinto fault zone shows the fault to be no older than 1.1 million to 1.3 million years and that its long-term slip rate is probably faster than previously thought.

Researchers at three universities conducted a National Science Foundation-funded study of the earthquake-active region, concluding that sedimentation related to slip in the San Jacinto fault zone began about 1 million years ago, significantly later than predicted by many models for faulting in southern California. Their findings appear in the November-December issue of the Geological Society of America Bulletin.

"Our findings suggest that the San Jacinto fault absorbs a large share of the relative motion between the Pacific and North American plates," said principal investigator Rebecca J. Dorsey, a professor of geological sciences at the University of Oregon. "This is important both for understanding the development of this active plate boundary and for helping to constrain estimates of seismic hazards in southern California."

Until now the birth of the San Jacinto fault in the area of Anza-Borrego Desert State Park had not been pinned down.

Geologists from the University of Oregon, Western Washington University and Utah State University carried out detailed geologic mapping, measuring and analysis of samples from Pleistocene (12,000 to 1.8 million years ago) sedimentary rocks in the western Salton Trough, including the Ocotillo Formation and the Font's Point Sandstone in the Borrego Badlands.

Using geologic, stratigraphic and paleomagnetic techniques, they determined that sedimentation related to slip in this fault zone began about 1 million years ago; the fault itself could have started a little earlier than that. A second fault reorganization about 400,000 years later produced a thin sheet-like alluvial deposit that created the Font's Point Sandstone, triggering modern uplift and erosion that has produced the popular Font's Point escarpment.

"The revised younger age of the San Jacinto fault indicates it is an important player in southern California's seismically active fault zones," Dorsey said.

However, she noted, "a rigorous assessment of long-term slip rate on this fault must await a complete analysis of the total offset on the fault," which already is underway. "Based on our current knowledge, it appears that the geologic slip rate could be as high as about 20 millimeters a year," she said.

Slip rate is the speed at which one side of a fault moves with respect to the other. Any rate over 10 millimeters a year is considered "fast," although the movement measured is an average occurring over long periods of time and many earthquakes. Previous studies concluded that fault has slipped about 25 kilometers (15.5 miles) in a right-lateral sense, at a rate of 10-12 millimeters a year during the last 2.0 million to 2.4 million years.

Jim Barlow | EurekAlert!
Further information:
http://www.uoregon.edu

More articles from Earth Sciences:

nachricht Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

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

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>