ad info

CNN.com
 MAIN PAGE
 WORLD
 ASIANOW
 U.S.
 LOCAL
 POLITICS
 WEATHER
 BUSINESS
 SPORTS
 TECHNOLOGY
   computing
   personal technology
   space
 NATURE
 ENTERTAINMENT
 BOOKS
 TRAVEL
 FOOD
 HEALTH
 STYLE
 IN-DEPTH

 custom news
 Headline News brief
 daily almanac
 CNN networks
 CNN programs
 on-air transcripts
 news quiz

  CNN WEB SITES:
CNN Websites
 TIME INC. SITES:
 MORE SERVICES:
 video on demand
 video archive
 audio on demand
 news email services
 free email accounts
 desktop headlines
 pointcast
 pagenet

 DISCUSSION:
 message boards
 chat
 feedback

 SITE GUIDES:
 help
 contents
 search

 FASTER ACCESS:
 europe
 japan

 WEB SERVICES:
Tech

Tsunamis threaten world's coastlines

August 25, 1998
Webposted at 11:50 AM EDT

By Environmental News Network staff


The New Guinea tsunami on July 17 started close to shore and damaged a relatively small, though heavily populated, area.
(ENN) -- Tsunamis, or tidal waves, may threaten more coastline regions around the world, including the West Coast of the United States, than previously thought, according to scientific team reporting on last month's tsunami in Papua New Guinea.

The team just returned from the Sissano Lagoon in northwestern Papua New Guinea and determined that July's devastating tsunami occurred when a 7.0 magnitude earthquake triggered a massive underwater landslide. The landslide created 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," he said.

"We probably have 10 earthquakes of that magnitude a year worldwide," said 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."


The death toll from the Papua New Guinea disaster will likely exceed 3,000 and be recorded as the deadliest tsunami of the century.
The researchers lament 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," said Synolakis.

Earthquakes of magnitude 7.5 and greater trigger tsunamis that traverse thousands of miles of ocean to affect thousands of miles of coastline, Synolakis said. In contrast, the New Guinea tsunami on 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 said.

"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," he said.

The researchers believe that an underwater landslide was involved in the tsunami because there is evidence of them occurring in the area, including a fresh one on a cliff at the western end of the survey area that locals say occurred during he earthquake, said Okal.

"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," he said.

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

Copyright 1998, Environmental News Network, All Rights Reserved

Related ENN stories:

Note: Pages will open in a new browser window

Latest Headlines

Today on CNN

Related sites:

External sites are not
endorsed by CNN Interactive.

SEARCH CNN.com
Enter keyword(s)   go    help

  
 

Back to the top
© 2000 Cable News Network. All Rights Reserved.
Terms under which this service is provided to you.
Read our privacy guidelines.