SAN FRANCISCO — If you wonder whether our fractious world could unite for a common purpose, take a look at this map. For the first time, the whole world has a scientifically sound chart of earthquake hazards on which to base safer building codes. It took unprecedented international cooperation to produce it.
"We had entire continents working together," says map coordinator Domenico Giardini. That includes regions where he says "politics are troubling," such as the seismically active borders between Turkey and Iran or between India and China. Some nations contributed information they had considered state secrets.
France, for example, handed over closely guarded data on seismic hazards at its nuclear power-plant sites. US Geological Survey seismologist Kaye Shedlock says that, although there were times when negotiations were rough, in the end, "we have everything we need."
Dr. Shedlock explains that the incentive for cooperation was the realization by national governments that "we want to be part of this." The map is global. But its benefits are realized locally. Some countries such as the United States or Japan don't need this map for internal purposes. They already know their seismic hazard. But, considering the aid they give to quake-stricken nations, they have a stake in every region's earthquake safety. And for many countries, this is the first modern scientifically sound seismic-hazard map they have ever had.
In explaining the benefits at a recent meeting of the American Geophysical Union in San Francisco, Dr. Giardini and Shedlock drew a distinction between "hazard" and "risk." The map shows the probability of severe horizontal ground shaking over the next 50 years. That's hazard. Seismic risk is the probability of such ground shaking causing damage. Frequent large earthquakes in sparsely populated areas pose severe seismic hazard, but little risk. There's not much to damage. Frequent smaller quakes in densely populated areas have lower seismic hazard, but high risk of damage. The map shows local authorities the degree of ground-shaking hazard to which they are exposed. They then can design appropriate building codes.
A glance at the map shows the importance of this global seismic view. The brown and red zones of greatest hazard run along the boundaries where the planet's crustal plates meet and interact. Much of humanity lives along these same zones. Until now, many local populations were unaware of the hazard with which they are living. Now they can take that hazard into account.
This doesn't mean that people should abandon high-hazard areas. "You can live in tectonic safety if you have a well-built house," Giardini says. Shedlock explains that people living in the high-hazard areas should have site-specific risk assessments for their housing. That means detailed assessments of where to build and how to build safely. "Know your hazards and mitigate them," she says. "But ... live your lives."
Giardini, who is director of the Swiss Seismological Service in Zurich, and Shedlock from the US Geological Survey's Denver office, represent agencies that are distributing the Global Seismic Hazard Map (above).
The mapmaking was a project of the International Lithosphere Program under the United Nations International Decade for Natural Disaster Reduction. Nations funded their own contributions and sometimes helped less affluent partners. Various international organizations also helped cover the cost.
It took more than 500 scientists to lay out the chart. They worked with modern seismic data, old historical and literary records, and geological formations to assess the probable levels of ground shaking. Even the Bible was a useful resource. Shedlock noted that, for this purpose, the Bible is a regional earthquake catalogue with records that go back more than two millenniums.
(c) Copyright 2000. The Christian Science Publishing Society