A tsunami alert test buoy floating in the Pacific Ocean off of the coast of Monterey, Calif., reacted to an Oct. 16 Southern California earthquake. The buoy, deployed May 11, 1999, is one in a series deployed by the National Oceanic and Atmospheric Administration to provide early warning of tsunamis.

"Although there was no tsunami produced by the 7.0 earthquake, it did trigger the buoy and gave us an unexpected test of the system," said Eddie Bernard, director of NOAA's Pacific Marine Environmental Laboratory in Seattle, Wash. "The buoy system performed as designed."

The buoy's seafloor sensor was lifted by seismic waves from the earthquake, creating an amplified pressure change.

The buoys are part of the Deep Ocean Assessment and Reporting of Tsunamis program (DART), designed to provide as much warning as possible. The two warning centers, one each in Hawaii and Alaska, did not receive the data from the test buoy as they are in the process of installing the necessary software, so no warning action was taken. The data are available on the PMEL Web site.

Tsunamis are often caused by underwater earthquakes or landslides that trigger a series of traveling ocean waves of extremely long length. Tsunami waves can travel hundreds of miles, but may only have a wave height of a few feet or less. They cannot be felt aboard ships nor seen from the air in the open ocean.

They are a major threat to coastal communities because once they reach shore, tsunami waves can be as much as 100 feet high, although those much smaller also can be destructive to lives and property.

"The DART system is essential to provide early warning," Bernard said. "Hawaii needs three and one-half hours advance notice to evacuate its residents. By the time we can see a large tsunami wave, it is usually to late too warn people."

The last destructive tsunami struck a village in northern Papua New Guinea in 1998, killing 2,000, mostly children home for school holidays.

DART provides information to the Tsunami Warning System, composed of 26 participating international member states. The Pacific Tsunami Warning Center, located in Honolulu, Hawaii, is the operational center of the Pacific Tsunami Warning System and provides tsunami warning information to national authorities in the Pacific Basin. NOAA operates a warning center in Alaska that provides warnings to Alaska, California, Oregon and Washington.

While tsunamis more often occur in the Pacific, they have caused damage in the Caribbean and Mediterranean Seas.

NOAA is one of the participating agencies in the U.S. National Tsunami Hazard Mitigation Program, a federal/state partnership that also includes the Federal Emergency Management Agency, the U.S. Geological Survey, and the states of Alaska, Washington, Oregon, California and Hawaii.

For information on the National Tsunami program, visit:
http://www.pmel.noaa.gov/tsunami-hazard/

Real-time data from the buoys can be found by clicking on the real-time data button on the above page.