Featured Research

from universities, journals, and other organizations

Scientific Team Returns From Tsunami Site

Date:
August 24, 1998
Source:
University Of Southern California
Summary:
The first scientific team to survey and report on last month's catastrophic tsunami at Sissano Lagoon in northwestern Papua New Guinea suggests that tsunamis, or tidal waves, may threaten more coastline regions of the world than previously thought, including much of the West Coast.

The New Guinea Tsunami Catastrophe Suggests Rising Peril For Pacific Rim & Other Coastline Regions

Related Articles


The first scientific team to survey and report on last month's catastrophic tsunami at Sissano Lagoon in northwestern Papua New Guinea suggests that tsunamis, or tidal waves, may threaten more coastline regions of the world than previously thought, including much of the West Coast.

The team believes that the tsunami occurred when a 7.0 magnitude earthquake triggered a massive underwater landslide--creating a series of waves that swept across heavily populated shoreline strips at the lagoon's entrance.

"We used to think a magnitude 7.0 earthquake was too small to generate a tsunami," says Costas Synolakis, Ph.D., leader of the four-person team funded by the National Science Foundation to measure the tsunami's inundation heights and inland penetration distances. "Of the nine large tsunamis that have occurred in the past six years, only the New Guinea one resulted from an earthquake as small as magnitude 7.0."

"We probably have 10 earthquakes of that magnitude a year worldwide," says team member Emile Okal, Ph.D. "You can have a very large danger concentrated in a very small area because of the instability of submarine structures that we do not have very well mapped."

Like Dr. Okal, Dr. Synolakis laments the world's lack of knowledge about ocean-floor topography. "We have a better map of the surface of Venus than we do of our own ocean floor," he says.

The American team consisted of Synolakis, a professor of civil engineering at the University of Southern California's School of Engineering; Okal, a professor of geophysics at Northwestern University; Boyd C. Benson, a graduate student at the University of Washington; and José C. Borrero, an NSF fellow and graduate student from USC.

Also accompanying the team was Mr. Borrero's father, José L. Borrero, M.D., a physician from Altamonte Springs, Fla., who treated survivors of the tsunami. Randy Sherman, M.D., chief of the division of plastic and reconstructive surgery at the USC School of Medicine, assembled medical supplies for the team physician.

Earthquakes of magnitude 7.5 and greater trigger tsunamis that traverse thousands of miles of ocean to affect thousands of miles of coastline, Synolakis notes. In contrast, the New Guinea tsunami of July 17 started close to shore and damaged a relatively small, though heavily populated, area.

Many seismically active coastlines of the Pacific Rim are comparable to the New Guinea disaster site, where the ocean floor declines rapidly close to shore, falling away in precipitous chasms and steep canyons.

"The Cascadia Subduction Zone off the state of Washington threatens British Columbia, Washington, Oregon and the northern California coastlines," Synolakis says.

"Southern California, because of its population density and offshore topography, is also threatened. It would not take a large tsunami to cause a disaster here, where hundreds of thousands of people are often at the beach. If you're at the beach and feel an earthquake, you should move to higher ground as quickly as possible."

Synolakis relates some of the New Guinea survey findings:

"A 7.0 earthquake, with the epicenter significantly inland, occurred shortly after sundown and was followed 20 minutes later by a 5.9 aftershock. We think the initial quake triggered a landslide on the sea floor, probably on the order of four or five cubic kilometers. The wave arrived onshore 5 to 10 minutes after the initial quake.

"Two large tidal waves were followed by a third and smaller wave. Initially no more than two or three meters high, the waves gained height as they raced over steeply decreasing depths toward the shore.

"On touching land, the largest waves were 10 to 14 meters (32 to 46 feet) high at the center (the maximum height fell off significantly a short distance from each wave's center) and 20 kilometers (12 miles) long. The mass of water in each wave extended back from the crest as far as four kilometers (2.5 miles).

"The water surged over the peninsula at an estimated speed of 10 to 20 meters per second, or 22 to 44 miles per hour. This force induced by the tsunami current is 1,000 times greater than the force of a wind of the same speed."

Okal points out three reasons why the researchers have inferred that an underwater landslide was involved in this tsunami: "One, we can't explain the size of the tsunami otherwise. Two, we know submarine landslides have occurred in other areas, since they're conspicuous on the ocean floor in other subduction zones. And three, we found a landslide above sea level while we were there. A cliff at the western end of our land survey area showed a big landslide that was extremely fresh. People told us it went down during the earthquake of July 17."

Okal concedes it's a big jump to the conclusion that the same thing happened below the sea. "But certainly," he argues, "in terms of the accelerations and the intensity of motion, what took place under the water was probably the same as what took place next door above the water, and if the material had the same level of instability, one could imagine a submarine landslide."

To study the causation of future tsunamis more accurately, Okal says, scientists really need to map the sea floor with radar, sonar, etc., from an oceanographic ship to look for evidence of a fresh underwater landslide.

At the request of Papua New Guinea authorities, the American scientists appeared at a public meeting to allay survivors' fears about returning to their homes and to quash some wild rumors about the disaster's cause. Many survivors believed they were being punished for impiety and that more waves were imminent. One 15-year-old girl asked why eyewitnesses had described the tsunami as "an infernal mountain of water with fire sparkles flying" -- a description consistent with the severe burns observed among many of the dead.

Synolakis says the rapid rise in sea level occasioned by the tsunami may have enhanced the bioluminescence of dinoflagellates and other glowing organisms commonly found in the waters of the South Pacific. "The tsunami occurred about an hour after sundown," he explains. "In the darkness, the organic bioluminescence may well have caused the water to sparkle like fire."

He says the burns seen on bodies resulted from friction when people were dragged over hundreds of meters of sand, debris and trees, and from the sunburn as they lay decomposing after the disaster, giving the appearance of death by scalding.

Synolakis says that the death toll from the Papua New Guinea disaster will likely exceed 3,000 and be recorded as the deadliest tsunami of the century.

For further information and pictures of the Papua New Guinea tsunami, point your browser to http://www.usc.edu/dept/tsunamis/PNG/PNG1.html.


Story Source:

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


Cite This Page:

University Of Southern California. "Scientific Team Returns From Tsunami Site." ScienceDaily. ScienceDaily, 24 August 1998. <www.sciencedaily.com/releases/1998/08/980824072053.htm>.
University Of Southern California. (1998, August 24). Scientific Team Returns From Tsunami Site. ScienceDaily. Retrieved October 26, 2014 from www.sciencedaily.com/releases/1998/08/980824072053.htm
University Of Southern California. "Scientific Team Returns From Tsunami Site." ScienceDaily. www.sciencedaily.com/releases/1998/08/980824072053.htm (accessed October 26, 2014).

Share This



More Earth & Climate News

Sunday, October 26, 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