Coastal Services Center

On April 1, 1946, a magnitude 7.1 earthquake in the Aleutian Islands off the coast of Alaska generated a tsunami that five hours later struck the Hawaiian Islands with waves of 20 to 32 feet. The tsunami claimed the lives of 159 people and caused $26 million in damage.

At 1:05 a.m. on May 23, 1960, 15 hours after a magnitude 9.5 earthquake struck offshore of Chile, a tsunami crashed into Hilo, Hawaii, killing 61 people and destroying 537 homes and businesses. Cost of the damage totaled over $23 million.

On November 29, 1975, a magnitude 7.2 earthquake occurred locally in the area of Kalapana, Hawaii, that within minutes generated a tsunami that reportedly reached heights of 47 feet. As a result of the earthquake and tsunami, two people were killed, including the leader of a Boy Scout troop on a camping trip, and $4.1 million was done in property damage.

It is only a matter of time before another tsunami strikes the Hawaiian Islands or elsewhere along the nation's shoreline. Since the last tsunami catastrophe in the U.S., development along the coastlines has skyrocketed, as have the potential damages.

Hawaii has worked hard to prepare the islands and its people for the inevitable wave that will come and has joined other Pacific states and the federal government in an effort to help save lives and property when the next tsunami does strike.

Knowing the Risk

Ten major tsunamis over the past decade have occurred in the Pacific basin, killing more than 4,000 people. Since 1900, tsunami events affecting the U.S. and its territories have been responsible for almost 470 fatalities and hundreds of millions of dollars in property damage.

The Hawaiian Islands, in particular, lie directly in the path of tsunamis created by most of the Pacific Ocean's subduction zones.

"Tsunamis are Hawaii's number one natural disaster killer," says Brian Yanagi, Earthquake-Tsunami-Volcano program manager for Hawaii's State Civil Defense.

The Pacific Northwest states of Alaska, Washington, Oregon, and California are vulnerable to tsunamis, as are islands in the Caribbean.

Although tsunamis are rare along the Atlantic coastline, a severe earthquake on November 18, 1929, in the Grand Banks of Newfoundland generated a tsunami that caused considerable damage and loss of life at Placentia Bay, Newfoundland.

Wave after Wave

A tsunami, or "harbor wave" in Japanese, is a series of waves usually caused by underwater earthquakes and occasionally by underwater volcanic eruptions and landslides.

Sometimes incorrectly referred to as tidal waves, tsunamis can either be generated by a distant earthquake that occurs anywhere in the Pacific Rim, or local earthquakes that happen just offshore.

The impact of a tsunami is "very similar to a hurricane storm surge where you have abrupt flooding," says Eddie Bernard, director of the National Oceanic and Atmospheric Administration's (NOAA) Pacific Marine Environmental Laboratory in Seattle.

Unlike hurricanes, tsunamis can travel at speeds up to 600 miles per hour in the open ocean and cannot be felt by ships or seen from the air. An earthquake in the Pacific Rim could generate tsunamis that could damage multiple state coastlines.

Learning from Experience

"Hawaii is the most tsunami prepared of all states," Bernard acknowledges.

After the devastating losses from the 1946 and 1960 tsunamis, Hawaii built a statewide tsunami emergency response system. The system includes unified state and county emergency plans, evacuation maps that are published in telephone books, a coordinated statewide siren system tied into an emergency alert system, and frontline emergency response personnel, Yanagi says.

But since Hawaii has not experienced a tsunami in almost 30 years, the islands' collective guard may be down.

"An entire generation has grown up on the islands and has not observed or witnessed the destructive power of a tsunami," Yanagi says. "There is a tremendous public awareness learning curve we are always trying to overcome."

The National Tsunami Hazard Mitigation Program (NTHMP), a partnership created in 1996 between the five Pacific states, NOAA, the Federal Emergency Management Agency, and the U.S. Geological Survey to reduce tsunami hazards along U.S. coastlines, has reenergized Hawaii's tsunami mitigation efforts, Yanagi says.

A Burst of Energy

As a result of the funding and collaborative efforts coming out of the NTHMP, Hawaii has upgraded its state and county civil defense emergency operations centers, created a tsunami video and brochure, developed a tsunami curriculum for fourth and fifth graders, conducted training workshops for the media and tourist industry, and partnered with many organizations to help educate the public.

Much of this progress has been the work of the Hawaii Tsunami Technical Review Committee, which partners with the state coastal zone management program, as well as other state, county, and federal agencies and the scientific and emergency management communities, so that "the best available science can be understood and applied in the real world," says Ann Ogata-Deal, planning and policy analyst with the Hawaii Coastal Zone Management Program.

The committee's training programs have specifically targeted hotel security and management, and other representatives of the tourism industry. "We have a huge tourist population that, with the exception of the Japanese, knows very little about tsunamis," Yanagi says. It is the responsibility of a hotel's management to ensure that its guests get to safety when a tsunami evacuation order is issued.

Heed the Warning

Although Hawaii is fortunate to have a federal warning system and statewide tsunami emergency response system in place, the decision to order an evacuation is not easy and must be made quickly.

Kwok Fai Cheung, professor and chair of Ocean and Resources Engineering at the University of Hawaii, notes that tsunami evacuation takes about three hours. "If it takes a tsunami five hours to travel from Alaska to Hawaii, that means you only have two hours to decide if it's going to be a destructive tsunami or not."

A false alarm is costly and impacts the credibility of future warnings.

A major benefit of the NTHMP for the state has been the upgrade of the seismic network, enabling the tsunami warning centers in Alaska and Hawaii to locate and size earthquakes faster and more accurately, and the development of technology to measure tsunamis in the deep ocean.

This was proven on November 17, 2003, when an Alaskan tsunami warning was cancelled because real-time deep ocean data showed the tsunami would not be damaging, Bernard says. Canceling this warning averted an evacuation in Hawaii, saving the state an estimated $68 million in lost productivity.

Hawaii Sea Grant also is funding research efforts led by Cheung that will help improve prediction methods for tsunamis. A tsunami run-up simulation model, which when combined with an inundation risk assessment model, will help civil defense agencies develop better inundation maps and evacuation plans, issue warnings during a tsunami event, and plan for long-term coastal land use.

Out of Harm's Way?

Experts agree that it's not a question of "if" another tsunami will strike the U.S. coastline, but "when."

"The ultimate challenge for coastal resource managers and planners," notes Bernard, "is to move homes and people away from the coastline" and out of harm's way.

It was only after two devastating tsunamis that permanent land use changes were incorporated into the City of Hilo, Yanagi says. "They learned the hard way about land use planning for natural hazards."

Even though it is politically difficult to direct development away from the coast, Ogata-Deal hopes that it won't take another catastrophe for land use planners to incorporate hazards mitigation.

She notes that federally mandated state and county multihazard mitigation strategies will soon be complete.

The research and information that these mitigation strategies provide may help "persuade decision makers to open their minds to new approaches to mitigate natural hazards. Serious consideration of novel planning approaches is one of our greatest challenges, but holds the most promise for the future," she says.

For more information on tsunamis, go to www.geophys.washington.edu/tsunami/, www.csc.noaa.gov/products/tsunamis/, or www.tsunami.org. For more information on Hawaii's tsunami mitigation efforts, contact Brian Yanagi at (808) 733-4301, ext. 552, or byanagi@scd.hawaii.gov. You may also contact Ann Ogata-Deal at (808) 587-2804, or AOgata-Deal@dbedt.hawaii.gov. For information on the National Tsunami Hazard Mitigation Program, go to www.pmel.noaa.gov/tsunami-hazard/, or contact Eddie Bernard at (206) 526-6800, or Eddie.N.Bernard@noaa.gov.