Featured Research

from universities, journals, and other organizations

Slip Rate Of Southern California Fault May Be Faster Than Previously Believed

Date:
October 30, 2006
Source:
University of Oregon
Summary:
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.

A view of Font's Point, located along the San Jacinto Fault in Southern California, in the Anza-Borrego Desert State Park. A team of researchers, including Rebecca Dorsey at the University of Oregon, has found that fault reorganization 600,000 years ago began the process of a sheet-like alluvial deposit that formed the popular Font's Point escarpment.
Credit: Photo by Rebecca Dorsey

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.

Related Articles


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.

Coauthors of the study were Dorsey and former UO master's student Andrew T. Lutz, who is now with William Lettis and Associates, a San Francisco-based geological consulting company, Bernard A. Housen of Western Washington University in Bellingham and Susanne U. Janecke of Utah State University in Logan. The findings of this study are closely related to two companion studies in the same region that were recently completed by Alex Steely and Stefan Kirby, master's students working with Janecke at Utah State.


Story Source:

The above story is based on materials provided by University of Oregon. Note: Materials may be edited for content and length.


Cite This Page:

University of Oregon. "Slip Rate Of Southern California Fault May Be Faster Than Previously Believed." ScienceDaily. ScienceDaily, 30 October 2006. <www.sciencedaily.com/releases/2006/10/061023192613.htm>.
University of Oregon. (2006, October 30). Slip Rate Of Southern California Fault May Be Faster Than Previously Believed. ScienceDaily. Retrieved November 28, 2014 from www.sciencedaily.com/releases/2006/10/061023192613.htm
University of Oregon. "Slip Rate Of Southern California Fault May Be Faster Than Previously Believed." ScienceDaily. www.sciencedaily.com/releases/2006/10/061023192613.htm (accessed November 28, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Friday, November 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Japan's Mt. Aso Volcano Spews Rocks

Raw: Japan's Mt. Aso Volcano Spews Rocks

AP (Nov. 28, 2014) — A volcano in southern Japan is spewing volcanic magma rocks. A regional weather observatory says this could be Mt. Aso's first magma eruption in 22 years. (Nov. 28) Video provided by AP
Powered by NewsLook.com
Scientists Find Invisible Space Shield Protecting Earth

Scientists Find Invisible Space Shield Protecting Earth

Newsy (Nov. 27, 2014) — An invisible barrier is keeping dangerous super fast electrons from interfering with our atmosphere, but scientists aren't entirely sure how. Video provided by Newsy
Powered by NewsLook.com
Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Reuters - Innovations Video Online (Nov. 26, 2014) — Innovative recycling project in La Paz separates city waste and converts plastic garbage into school furniture made from 'plastiwood'. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Blu-Ray Discs Getting Second Run As Solar Panels

Blu-Ray Discs Getting Second Run As Solar Panels

Newsy (Nov. 26, 2014) — Researchers at Northwestern University are repurposing Blu-ray movies for better solar panel technology thanks to the discs' internal structures. Video provided by Newsy
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