Researcher Says Warning Systems Must Include Human Factors
Within days of the earthquake that struck northwest of Sumatra, Indonesia, triggering a tsunami that barreled across the Indian Ocean, the Pacific Tsunami Warning System, or PTWS, announced plans to expand its network to the Indian Ocean and other possible trouble spots. In place since 1949, the PTWS generates data about earthquakes and potential tsunamis in the Pacific area and disseminates that information to at-risk areas. On the PTWS Web site, officials said that such a system, had it been in place, could have significantly reduced the loss of life in Asia. But one psychologist believes it would have taken more than technology to avert the tragedy.
Roy Lachman, a University of Houston psychologist who experienced firsthand the effects of a tsunami while teaching at the University of Hawaii at Hilo, does not think a system that focuses mainly on the technological aspects of warning the public will effectively mitigate future loss of life, unless it takes into account how human beings respond to the information they are given.
“A relatively primitive warning system will save most lives if people know how to interpret it and how to respond; if they don’t, the most technically sophisticated warning system in the world will save no one,” Lachman said.
Lachman’s skepticism of warning systems that ignore human factors is founded on personal experience as much as psychological research. After a tsunami struck Hilo in May 1960, he and University of Hawaii colleagues William Bonk and Maurice Tatsuoka conducted what remains to this day the only systematic study of human behavior in the face of a threatening tidal wave.
A study of 327 people affected by the Hilo disaster concluded that an adequate prediction system existed but that the death toll was needlessly high because the population had trouble interpreting the warning. The research was published in the May 5, 1961 issue of Science.
The Hilo wave originated, as did the South Asian wave, with an undersea earthquake. At exactly 7:11 pm Greenwich Mean Time on May 22, 1960, an earthquake registering 8.6 on the Richter scale was recorded off the coast of South Central Chile, along the Peru-Chile trench some 20 miles below the surface. Within 20 minutes, a 75-foot tidal wave had struck the Chilean coastline nearest the epicenter, killing an unknown number of people there.
It would be another 15 hours before the wave, 35 feet high at impact, hit Hilo. When it did, upwards of 60 people were killed, hundreds were injured, and more than 1,000 were displaced.
Most, if not all, of the injuries and deaths were preventable, Lachman said. The time between the initial earthquake and the tsunami strike on Hilo was more than enough for area residents to move to higher ground, enough even for them to gather significant belongings before evacuating.
During that time, Hilo residents heard news reports of the Chilean disaster, and seismologists could readily predict the direction and size of the wave. Hawaii had a warning system, the PTWS, which had been set up several years after a devastating wave killed a number of schoolchildren in the little coastal town of Lapahoihoi in 1946.
In the 1960 incident, Hilo residents were notified of a tsunami threat by a siren that sounded for 20 minutes more than four hours before the wave hit. Most people took some action, and many even prepared to evacuate. Yet 60 percent of residents in the affected areas did not leave.
For the Science article, Lachman and his colleagues asked survivors of the Hilo tsunami what they had done in the hours between the Chilean earthquake and the early morning hours when the tsunami hit. They learned that 95 percent of the interviewees had heard the siren, and almost all of them reported that they knew what it meant. However, when asked what they had actually done, their responses varied so much that the researchers began to wonder what the siren officially meant, and what actions the population was expected to take when the siren sounded.
It was at this point that the flaws in the warning system became evident, Lachman said. “The telephone book, cited by civil defense authorities as the official medium for disseminating this information, merely described the siren as an ‘alert,’ with no instructions to the population as to what actions they should take upon being ‘alerted.’ As a result, people were left to figure out on their own what to do, perhaps to wait for more information as to the extent and location of the danger.”
To people reading about the South Asian tragedy, it might seem that the obvious thing to do is get to high ground, but according to Lachman that response is not intuitive to everyone. “Even the civil defense headquarters, located at a US armory building near the beach, was not evacuated,” he said. With a shake of his head, he recounted the story of the head of civil defense in Hilo, who realized he needed to be 50 feet above sea level but thought that meant “50 feet back from the water.”
With no official instructions and no clear sources of life-saving information, the people of Hilo were left to fend for themselves or turn to the radio or (for the few who had one in 1960) the television. Many simply waited for more official information, which never came.
Lachman said the unofficial information available was worse than none at all, for it was imprecise, raw, and uninterpreted. Survivor interviews revealed that many people understood that a tidal wave “might” be on the way, while others heard on the evening news that a rise of three feet had been reported in Tahiti, concluded that they were not in danger, and went to bed.
To a seismologist, a three-foot rise in Tahiti would foretell a monster wave in Hawaii, but the information was, as Lachman put it, “lost in translation.”
The tragedy in South Asia has reminded us that both coasts of the United States are also vulnerable to tsunamis. An article in the January 3, 2005 issue of The Australian recounts the problem of the Cumbre Vieja volcano, located on the Canary Island of La Palma. According to the article, Cumbre Vieja is known to have fragile fissures that will almost surely collapse in the event of an eruption, triggering a “catastrophic failure” of its western flank and dropping huge masses of rock into the sea.
The resulting water displacement would produce a tsunami that would hit nearby west Africa within an hour, with waves as high as 300 feet, and within a few more hours would dramatically affect the Atlantic coastal areas of Western Europe, Canada, and the United States.
After the Hilo disaster, the Hawaiian warning system was revised. Schoolchildren were given instructions and materials to take home to their parents, including specific instructions on how to respond to a tsunami warning. In 1968, a number of countries in the Pacific region developed the Intergovernmental Oceanic Commission to assure that their members had access to the seismological information from which tsunamis are predicted. Something similar will almost certainly be developed for the vulnerable states in the South Asian region, and perhaps worldwide, following the destruction of the recent wave.
Lachman said he strongly approves these efforts; however, he cautioned against too much emphasis on its technical and political aspects. He noted that new buildings, new commissions, and new appointees are highly visible and politically attractive, but as Hilo’s experience showed, they cannot save a single life unless the prospective evacuees know what to do when a wave is coming.
“When a wave is on the way, it is decisions made by ordinary people on the shoreline, not seismologists, politicians or engineers, that determine how dreadful the next week’s headlines will be,” Lachman said.
Editor’s Note: Dana Lachman is Roy Lachman’s daughter.
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