submarine landslide, the center might not detect this as a tsunami source. The scientific community is working on this problem and hopes to use global positioning satellites to see these submarine landslides even if there is no earthquake to trigger them. To address this problem in the interim, the center has written software that triggers the pagers if large amplitudes are detected on certain coastal water level gauges.

Finally, as Hirshorn pointed out to me, the Pacific Tsunami Warning Center is analogous to one leg of a three-legged structure. The other two legs are emergency management and public education and awareness. Without the other two “legs,” the center’s warnings are of little value. Once the center has sent out a warning, communities likely to be affected by the tsunami need to implement predetermined emergency procedures. Typically these will involve mobilization of police and other emergency services, beach clearance, sounding of sirens or alarms, and traffic control to permit prompt evacuation of low-lying areas.

Public education and awareness are essential. The public needs to be informed in order to evacuate promptly in the event of a major offshore earthquake or if the ocean is observed to suddenly recede. If a warning is given, people need to know the shortest route to high ground—and, after a wave has hit, to stay clear of low-lying areas because there are very likely to be many more waves on the way. There can be waves for hours after the initial wave hits, and often the first wave is not the largest.

The importance of public education was proven dramatically by the Papua New Guinea tsunami of July 17, 1998, which slaughtered 2,500 people—75 percent of the population in the coastal areas hit by the tsunami. When the next tsunami occurred, the death toll was drastically reduced—because a public education campaign had informed people of the warning signs and the steps to be taken to evacuate. Also, during the Southeast Asia tsunami of December 2004, fatalities were low on several Indian Ocean islands simply because the village elders saw the ocean waters withdrawing from the shore; recognized, thanks to village lore, that this phenomenon heralded a tsunami; and warned the populace to withdraw to high ground. Others were not so fortunate.

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