Future Quake Toll to Worsen, Experts Say

The death and devastation caused by major earthquakes around the world can only worsen in the years to come, as growing urban development and unprecedented population growth compound the lethal effects of natural seismic hazards, experts said Tuesday.

Big earthquakes strike the Earth with the regularity of an alarm bell--with about 18 earthquakes measuring 7.0 or greater every year on average, and four or five above the very dangerous 7.6 level. So the recent rash of destructive temblors in Turkey, Greece and now Taiwan does not signify any increase in quake activity.

What has changed, however, is that more and more people are living near faults. With the global population estimated to surpass 6 billion this year, there are fewer unpopulated quake-prone areas. With ever more people to accommodate, there is more multistory construction in vulnerable fault zones as well.

As a result, destructive earthquakes such as those of the past several weeks “are the wave of the future,” said Caltech seismic expert Kerry Sieh. “There are 40 cities of a million or more people within 100 kilometers of a major plate boundary, and all those are good candidates for a large event. Our exposure to the hazard is increasing.”

Moreover, some experts suggest that in recent decades the world has actually experienced a lull in the most severe earthquakes--those of magnitude 8.0 or greater. If so, even more destructive temblors are to be expected when the lull ends.

Although Taiwan is shaken by dozens of earthquakes every year, the tremor early Tuesday was the worst there since a magnitude 7.4 temblor in 1935, which killed 3,276 people. This week, more than 1,700 people died and 100,000 people were left homeless. At least 2,700 people were still missing.

The predawn quake was caused by the inexorable crush of two major tectonic plates that squeeze the island from the east and west at the relatively rapid rate of several centimeters a year, building up seismic energy like the tension in a coiled spring.

Southern California is caught in a similar tectonic vise that has generated about 300,000 earthquakes of measurable magnitude in the past 20 years, according to Caltech seismologist Egill Hauksson.

The disaster in Taiwan was the most recent in a series of damaging urban earthquakes in just over a decade.

Devastating tremors killed at least 16,000 people during a 7.4 earthquake in Turkey in August. At least 143 people died during a 5.9 temblor in Athens several weeks later. More than 6,400 people died in a 1995 quake in Kobe, Japan. The 1994 Northridge earthquake in Los Angeles and the 1989 Loma Prieta temblor near San Francisco were among the most costly natural disasters in U.S. history.

Millions of earthquakes occur around the world annually. Most are too small to be felt. An average of 3,000 magnitude 5.0 quakes are recorded each year.

The destruction caused by any single earthquake is unpredictable.

Tuesday’s Taiwanese earthquake, at 7.6, was roughly twice as powerful as the 7.4 quake that racked Turkey last month. But the death toll may be only one-tenth as high, in large part because construction codes in Taiwan were more strictly enforced than in Turkey, several experts said.

Other factors can also make a huge difference. Had the epicenter of the Northridge earthquake been located a few miles south, more directly under the downtown area, or had it occurred during the daytime, the death toll might have reached the thousands, rather than the dozens, with damage totaling $100 billion or more, several seismic hazard experts say. In the same vein, government officials in Taiwan on Tuesday said the temblor could have been even more deadly had its timing and location been slightly different.

“We roll the dice every time,” said earthquake hazard analyst Charles Kircher in Mountain View, Calif.

But as urban boundaries expand to encompass growing populations, those dice are being weighted for disaster. “We get closer to known faults and put more people on top of the faults,” Kircher said.

“There has been a fourfold increase in the world’s population since the 1906 San Francisco quake, and, if you look at the numbers, most of the million people who have died this century in earthquakes have died in poorly built urban areas.”

While better construction can clearly save many lives, some experts worry that quake-specific engineering solutions will foster the belief that it is safe to build in areas with large quake hazards--thereby making the long-term hazard worse.

“We think technology can make us totally safe, independent of the planet we live on,” said Dennis Mileti, a sociologist who directs the University of Colorado’s Natural Hazards Center in Boulder and was lead author of a recent government analysis of natural disaster risks. “The problem with that approach is that there is always an event in nature that exceeds what we designed for.”

Consequently, “almost everything we do to protect ourselves only ends up postponing losses into the future,” Mileti said. “When a larger event in nature comes along, there is more to lose.”

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Taiwan Quakes

Taiwan experiences dozens of earthquakes a year, most in the Pacific Ocean east of the island. Tuesday’s 7.6 quake in the center of the country has left at least 1,700 dead, hundreds missing and more than 100,000 without homes. Shown here are large quakes from 1604 to the present.

Source: Hiroshima University