Featured Research

from universities, journals, and other organizations

Folded Sediment Unusual In Sumatran Tsunami Area

Date:
February 4, 2007
Source:
Penn State
Summary:
Sediment folding may have added to the exceptionally large tsunami that struck Sumatra on December 26, 2004, according to an international team of geologists.

Sediment folding may have added to the exceptionally large tsunami that struck Sumatra on Dec. 26, 2004, according to an international team of geologists. "Tsunami models consider the rebound of the plate during the earthquake, but do not include permanent deformation, like folding, of the upper plate." says Dr. Donald M. Fisher, professor of geosciences at Penn State.

Tsunamis propagate only when earthquakes occur under water and have an up and down component to their motion. Earthquakes where tectonic plate boundaries slide side by side, do not cause tsunamis. Subduction zone earthquakes, those areas where one plate moves beneath another, are prime candidates for tsunami generation, but if the two plates slide smoothly across each other, water is displaced very slowly.

"If a fault is not locked, the two plates just creep along and there is no big upsurge," says Fisher. "However, if they are locked, the bottom plate drags the top plate along until it snaps back and quickly displaces water."

An expedition, organized by the Discovery Channel and BBC-TV, explored the 136-mile area of the fault using seismic reflection, a system where a sound source activates beneath the water and researchers record the time the sound takes to reach the underwater receivers. This process provides a detailed map of the sea bottom and the terrain beneath it. The researchers reported their work in a recent issue of Geology.

The researchers, who included Fisher; David Mosher, Geological Survey of Canada -- Atlantic who supplied the seismic reflection equipment; James A. Austin Jr., senior research associate and Sean P.S. Gulick, research associate, University of Texas, Austin; Timothy Masterlark, assistant professor, University of Alabama, and Kathryn Moran, associate professor, University of Rhode Island, found that the shape of the upper plate boundary was unusual.

"The fault line does not look as we assumed it did," says Fisher. "We expected a wedge with one plate going under the other."

The Sumatran plate boundary looked, in many ways, like the cabling on a suspension bridge. The area near the edge did form a wedge, but the central portion was framed by two peaks with a sway or saddle in the middle, with the farthest part then sloped downward. The central swayback portion was also populated by bumps located about 8 miles apart across its length.

"We also found that this is a blind fault, one that is not visible at the surface because it is covered in a deep layer of silt and sediment," says Fisher. "The peaks every 8 miles were caused when an earthquake folded the sediment."

These peaks add to the amount of water displaced when the entire plate edge snaps back. The fold spacing shows that the sediments are from 1 to 3 miles deep. The researchers suggest that the sediment deforms independently from the actual plate boundary.

The researchers conclude that the combination of processes, plate edge movement and snap back and the deformation of the sediment combines to enhance the uplift on a substantial portion of the fault and has important implications for evaluation of the 2004 tsunami and others that occur in this location.


Story Source:

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


Cite This Page:

Penn State. "Folded Sediment Unusual In Sumatran Tsunami Area." ScienceDaily. ScienceDaily, 4 February 2007. <www.sciencedaily.com/releases/2007/02/070203103432.htm>.
Penn State. (2007, February 4). Folded Sediment Unusual In Sumatran Tsunami Area. ScienceDaily. Retrieved July 24, 2014 from www.sciencedaily.com/releases/2007/02/070203103432.htm
Penn State. "Folded Sediment Unusual In Sumatran Tsunami Area." ScienceDaily. www.sciencedaily.com/releases/2007/02/070203103432.htm (accessed July 24, 2014).

Share This




More Earth & Climate News

Thursday, July 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Observation Boat to Protect Cetaceans During Ship Transfer

Observation Boat to Protect Cetaceans During Ship Transfer

AFP (July 22, 2014) As part of the 14-ship convoy that will accompany the Costa Concordia from the port of Giglio to the port of Genoa, there will be a boat carrying experts to look out for dolphins and whales from crossing the path of the Concordia. Duration: 01:02 Video provided by AFP
Powered by NewsLook.com
New Orleans Plans to Recycle Cigarette Butts

New Orleans Plans to Recycle Cigarette Butts

AP (July 21, 2014) New Orleans is the first U.S. city to participate in a large-scale recycling effort for cigarette butts. The city is rolling out dozens of containers for smokers to use when they discard their butts. (July 21) Video provided by AP
Powered by NewsLook.com
Shark Sightings a Big Catch for Cape Tourism

Shark Sightings a Big Catch for Cape Tourism

AP (July 21, 2014) A rise in shark sightings along the shores of Chatham, Massachusetts is driving a surge of eager vacationers to the beach town looking to catch a glimpse of a great white. (July 21) Video provided by AP
Powered by NewsLook.com
Spectacular Lightning Storm Hits London

Spectacular Lightning Storm Hits London

AFP (July 19, 2014) A spectaCular lightning storm struck the UK overnight Friday. Images of lightning strikes over the Shard and Tower Bridge in central London. Duration: 00:23 Video provided by AFP
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