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"Supercities" Vulnerable to Killer Quakes, Expert Warns

By John Roach
for National Geographic News
May 2, 2003
 
Unless protective measures are taken, once every century or so when the Earth trembles in a violent release of pent up tension, buildings will tumble, streets will buckle, and pipelines will snap, leaving upwards of a million people crushed beneath the debris.

That is the conclusion of Roger Bilham, a geological scientist at the University of Colorado at Boulder who studied the potential impact of earthquakes on the world's rapidly expanding urban populations in the 21st century.

To avoid such catastrophes, earthquake-resistant construction practices must be adopted and enforced around the world, said Bilham, who is a fellow in the university's Cooperative Institute for Research in Environmental Sciences.


"Most countries have earthquake resistant codes," he said. "The problem is often a matter of enforcing them."

Many of the world's largest so-called "supercities" with populations of 2 million to 15 million are located near fault zones that have caused major earthquakes in the past. Population in many of these cities is expected to continue expanding.

Earthquake experts from around the world tend to agree with Bilham's suggestion that the consequences of a major earthquake in the region of one of the world's major cities would be dire.

"As population grows, and it is growing in earthquake-prone regions, we are susceptible to large earthquakes causing huge numbers of fatalities," said Andy Michael, a geologist with the U.S. Geological Survey's Western Earthquakes Hazard Team in Menlo Park, California.

"People do not like to think in terms of an earthquake disaster of 1 million fatalities. Nevertheless, I am convinced this is possible," said Max Wyss, director of the World Agency of Planetary Monitoring and Earthquake Risk Reduction in Geneva, Switzerland.

Brian Tucker, president of GeoHazards International, said his Palo Alto, California-based nonprofit organization was established in 1991 to address "precisely" the type of problems that Bilham suggests are possible.

"Of course, exactly how many people will die in the next large earthquake and how often these earthquakes will occur cannot be known," said Tucker. Regardless, he added, it is clear that the consequences will have a large human, economic, and political effect on the entire world.

Population Growth

Prior to the 17th century, few cities had populations greater than 1 million people, said Bilham. By 1950 there were 43 supercities. Today there are nearly 200 supercities and that number could double before world populations stabilize.

"There is no question about the fact that population growth, the recent and coming population growth, is concentrated in developing countries and a lot of these are in earthquake-threatened areas," said Tucker.

According to Balham's study, which was to be presented May 2 in San Juan, Puerto Rico at the Seismological Society of America's annual meeting, roughly 8 million people have died as a result of building collapses in the past thousand years.

Ian Main, a professor of seismology and rock physics at the University of Edinburgh in Scotland, said, "the problem is not that there are more earthquakes nowadays. The problem is one of increasing vulnerability of the population, particularly in megacities built close to plate boundaries."

Bilham's calculations show that each year an earthquake kills 100 people, every two years an earthquake kills 1,000 people, every five years an event kills 10,000 people, and every century an earthquake kills 300,000.

"But the 300,000 people is probably an underestimate because the size of these huge cities doubled in the last century and are expected to double again in the next century," he said in a statement. "We have never had such a devastating megaquake before because it simply wasn't possible. But now we have more target cities that are bigger than ever before."

According to Bilham, nearly half of the modern supercities are located within 120 miles (200 kilometers) of a major plate boundary or the site of a historically damaging earthquake. Some of the more vulnerable cities include Tehran, Iran (population 6.7 million); Jakarta, Indonesia (9.1 million); and Mexico City (18.2 million).

"[These] cities are at great risk because of the large population, low quality construction in places, and potential for frequent earthquakes," Bilham told National Geographic News.

The deadliest earthquake on record, according to the U.S. Geological Survey's Andy Michael, was in Tangshan, China, in 1976. The official death toll is 255,000, but "the estimate could be as high as 655,000," he said. "This lends credibility to the conclusion that a million in an earthquake is conceivable."

Earthquake Safety

People in earthquake-prone cities of the western U.S. like Los Angeles and San Francisco live in flexible wood frame houses and earthquake-resistant building codes are enforced, said Bilham.

"Earthquakes in the US kill few people but cost a lot in cosmetic repairs. Earthquakes in developing countries tend to respond with widespread collapse, numerous fatalities," he said.

The problem in much of the developing world is that meeting the demand for housing or schools is more important than the safety of the people or the durability of their structures. As a result, Bilham said that contracts are awarded to the lowest bidders.

"I consider it shameful that a technological society like ours continues to construct buildings that are unsafe," he said. "But I am optimistic that we shall change our ways. We are entering what I believe future generations will call the age of construction."

Bilham expects world population to double in the next 50 years, meaning the construction of as many dwellings in the next 50 years as already exist. "Many of these will be three and four story apartments. We have an opportunity to construct them so they don't fall down."

Tucker said that Bilham's conclusions should concern not only people in the developing countries but people around the world. For example he said that predictions for the next big earthquake in Tehran, Iran, could result in as many as 300,000 deaths.

"Apart from its economic impact, apart from its humanitarian impact, such an earthquake could destabilize that government," said Tucker. "And that area needs some stability."

Steps to reduce the threat to supercities posed by earthquakes in developing countries include raising worldwide awareness of the problem and then working with local affected communities to reinforce their schools, said Tucker.

"You can mobilize people to spend labor and money strengthening their schools and once that is done it starts to raise consciousness of the problem, which creates a demand to improve other buildings in the community," he said.

In addition to condemning or strengthening at risk schools, hospitals and government buildings, Wyss said it is important to educate people on how they can avoid injuries in their homes and to increase the preparedness of rescue teams.

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