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.

Related Articles


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 October 25, 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 October 25, 2014).

Share This



More Earth & Climate News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

EU Gets Climate Deal, UK PM Gets Knock

EU Gets Climate Deal, UK PM Gets Knock

Reuters - Business Video Online (Oct. 24, 2014) EU leaders achieve a show of unity by striking a compromise deal on carbon emissions. But David Cameron's bid to push back EU budget contributions gets a slap in the face as the European Commission demands an extra 2bn euros. David Pollard reports. Video provided by Reuters
Powered by NewsLook.com
Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Raw: Tornado Rips Roofs in Washington State

Raw: Tornado Rips Roofs in Washington State

AP (Oct. 24, 2014) A rare tornado ripped roofs off buildings, uprooted trees and shattered windows Thursday afternoon in the southwest Washington city of Longview, but there were no reports of injuries. (Oct. 24) Video provided by AP
Powered by NewsLook.com
Fast-Moving Lava Headed For Town On Hawaii's Big Island

Fast-Moving Lava Headed For Town On Hawaii's Big Island

Newsy (Oct. 24, 2014) Lava from the Kilauea volcano on Hawaii's Big Island has accelerated as it travels toward a town called Pahoa. 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