Featured Research

from universities, journals, and other organizations

Using new technique, scientists find eleven times more aftershocks for 2004 quake

Date:
November 24, 2009
Source:
Georgia Institute of Technology
Summary:
Using a technique normally used for detecting weak tremor, scientists have discovered that the 2004 magnitude 6 earthquake along the Parkfield section of the San Andreas fault exhibited almost 11 times more aftershocks than previously thought.

Using a technique normally used for detecting weak tremors, scientists at the Georgia Institute of Technology discovered that the 2004 magnitude 6 earthquake along the Parkfield section of the San Andreas fault exhibited almost 11 times more aftershocks than previously thought.

The research appears online in Nature Geoscience and will appear in print in a forthcoming edition.

"We found almost 11 times more events in the first three days after the main event. That's surprising because this is a well-instrumented place and almost 90 percent of the activity was not being determined or reported," said Zhigang Peng, assistant professor at Georgia Tech's School of Earth and Atmospheric Sciences.

In examining how these aftershocks occurred, Peng and graduate research assistant Peng Zhao discovered that the earliest aftershocks occurred in the region near the main event. Then with time, the aftershocks started migrating. Seeing how the aftershocks move from the center of the quake outward lends credence to the idea that it's the result of the fault creeping, said Peng.

"Basically, the big event happens due to sudden fault movement, but the fault doesn't stop after the main event. It continues to move because the stress has been perturbed and the fault is trying to adjust itself. We believe this so-called fault creep is causing most of the aftershocks," he said.

Peng and Zhao used a method known as the matched filter technique, rather than the standard technique to examine the aftershocks. The traditional way of determining a location of an earthquake is that a human analyst has to go through each seismic recording, determine the order of events and their location. This takes time and if there are many events, or if some of them occur at the same time, it's hard for the analyst to figure out which came first.

"Because of these difficulties, only the largest aftershocks are located, with many small ones missing. So, we used the matched filter technique because it allows us to use a computer to automatically scan the seismic records to detect events when their patterns are similar. There is no need to manually pick out the aftershocks after the mainshock," said Peng.

The team chose the 2004 Parkfield quake to test the matched filter technique because the quake is on the San Andreas fault. The San Andreas is one of the most heavily instrumented places in the world, owing to the famous Parkfield, California, earthquake prediction experiment in the 1980s.

Peng is currently using the matched filter technique to work with several other research groups to detect early aftershocks of recent large earthquakes in Japan and China.


Story Source:

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


Cite This Page:

Georgia Institute of Technology. "Using new technique, scientists find eleven times more aftershocks for 2004 quake." ScienceDaily. ScienceDaily, 24 November 2009. <www.sciencedaily.com/releases/2009/11/091123114644.htm>.
Georgia Institute of Technology. (2009, November 24). Using new technique, scientists find eleven times more aftershocks for 2004 quake. ScienceDaily. Retrieved April 24, 2014 from www.sciencedaily.com/releases/2009/11/091123114644.htm
Georgia Institute of Technology. "Using new technique, scientists find eleven times more aftershocks for 2004 quake." ScienceDaily. www.sciencedaily.com/releases/2009/11/091123114644.htm (accessed April 24, 2014).

Share This



More Earth & Climate News

Thursday, April 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

UN Joint Mission Starts Removing Landmines in Cyprus

UN Joint Mission Starts Removing Landmines in Cyprus

AFP (Apr. 23, 2014) — The UN mission in Cyprus (UNFICYP) led a mine clearance demonstration on Wednesday in the UN-controlled buffer zone where demining operations are being conducted near the Cypriot village of Mammari. Duration: 01:00 Video provided by AFP
Powered by NewsLook.com
California Drought Is Good News for Gold Prospectors

California Drought Is Good News for Gold Prospectors

AFP (Apr. 22, 2014) — For months California has suffered from a historic drought. The lack of water is worrying for farmers and ranchers, but for gold diggers it’s a stroke of good fortune. With water levels low, normally inaccessible areas are exposed. Duration: 01:57 Video provided by AFP
Powered by NewsLook.com
Raw: MN Lakes Still Frozen Before Fishing Opener

Raw: MN Lakes Still Frozen Before Fishing Opener

AP (Apr. 22, 2014) — With only three weeks until Minnesota's fishing opener, many are wondering if the ice will be gone. Some of the Northland lakes are still covered by up to three feet of ice, causing concern that just like last year, the lakes won't be ready. (April 22) Video provided by AP
Powered by NewsLook.com
Scientists Warn Of Likely El Niño Event This Year

Scientists Warn Of Likely El Niño Event This Year

Newsy (Apr. 22, 2014) — With Pacific ocean water already showing signs of warming, the NOAA says there's about a 66 percent chance the event will begin before November. 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:
from the past week

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