Study: Calif.Threatened by Tsunamis

S A N   F R A N C I S C O, Dec. 19 -- Tsunamis generated by underwater landslidespose a serious threat to coastal communities in California andelsewhere, say researchers who are trying to determine wheresubmarine slips are most likely to occur.

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

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

“The biggest thing about local tsunamis is that they’resurprising,” said Philip Watts, president of Applied FluidsEngineering Inc. in Long Beach. “Coastal residents need to beeducated about the hazards.”

Sea Floor Maps

On Monday, experts in the budding field of tsunamis and undersealandslides gathered at the fall meeting of the American GeophysicalUnion to discuss early attempts to locate hazardous areas andassess risk, particularly in Southern California.

Detailed maps of the sea floor are still being collected andanalyzed for evidence of past landslides and tsunamis. Researchershope to eventually predict the likelihood, location, size andmotion of future landslides, and the size of waves given thosefactors.

Shortly after the Papua New Guinea disaster, researchers beganlooking more carefully at the sharp undersea cliffs and canyons offthe coast of California, particularly at the southern end of thestate.

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

Along the Santa Barbara Basin, a more than 80-square-milesection of sea canyon wall slid near Goleta. The area of failure is9 miles long, 6.5 miles wide. The area fell more than 1,500 feet.

“We were surprised to see the extent and complexity of apparentmass sea floor wasting in the Santa Barbara Basin,” said GaryGreene of the Monterey Bay Aquarium Research Institute, which ledthe research.