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SAN FRANCISCO — Tsunamis generated by underwater landslides pose a serious threat to coastal communities in California and elsewhere, say researchers who are trying to determine where submarine slips are most likely occur. 

Until recently, experts believed tsunamis were caused by distant undersea earthquakes or volcanoes. That changed in 1998, when a quake-triggered underwater landslide generated a 50-foot wave that killed 2,200 people on the coast of Papua New Guinea. 

Unlike tsunamis unleashed by distant quakes, locally generated tsunamis give only a few minutes warning before landfall. 

“The biggest thing about local tsunamis is that they’re surprising,” said Philip Watts, president of Applied Fluids Engineering Inc. in Long Beach. “Coastal residents need to be educated about the hazards.” 

On Monday, experts in the budding field of tsunamis and undersea landslides gathered at the fall meeting of the American Geophysical Union to discuss early attempts to locate hazardous areas and assess risk, particularly in Southern California. 

Detailed maps of the sea floor are still being collected and analyzed for evidence of past landslides and tsunamis. Researchers hope to eventually predict the likelihood, location, size and motion of future landslides, and the size of waves given those factors. 

Shortly after the Papua New Guinea disaster, researchers began looking more carefully at the sharp undersea cliffs and canyons off the coast of California, particularly at the southern end of the state. 

Collapses stretching for miles were found in at least two areas, near Santa Barbara and the Palos Verdes Peninsula in Los Angeles County. 

Along the Santa Barbara Basin, a more than 80-square-mile section of sea canyon wall slid near Goleta. The area of failure is nine miles long, 6.5 miles wide. The area fell more than 1,500 feet. 

“The hazard is there. We aren’t able to quantify it at the moment,” he said. “The basic thing we did was to show there have been some landslides in the past. Why wouldn’t there be any in the future?” 

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On the Net: 

Applied Fluids Engineering Inc.: http://www.appliedfluids.com 

International Tsunami Information Center: http://www.shoa.cl/oceano/itic/frontpage.html