Lab Notes
Superbuildings Shake It Up

On Monday, Dec. 22, 2003, 16 kilometers beneath the Earth's surface, a hill-sized spur of rock gave way between two grinding tectonic plates, relieving the pressure between them and releasing the energy equivalent of a 5-megaton H-bomb. Above the break, the planet's stiff crust rang like a bell, then rippled like a glass of water in the vicinity of a stomping T-rex. The result—an earthquake measuring 6.5 on the Richter scale—shook the small town of Paso Robles to its foundations, collapsing a 19th-century clock tower and killing two women who might otherwise have lived on for decades. The world is sadly poorer for this loss.

Still, Richter 6.5 is generally considered a minor earthquake, while the word "major" is reserved for magnitudes of 7 and above, and "catastrophic" for magnitudes of 8 and 9 (equivalent to 1,000 megatons and 32,000 megatons, respectively). Why, then, did 30,000 people die in the Iranian city of Bam just four days later, when a magnitude 6.3 quake burst out from the same depth, in geologically similar terrain? How can a "minor" earthquake cause 10 times as much destruction and heart-wrenching tragedy as the 1906 San Francisco earthquake and fire—the deadliest quake in U.S. history?

The answer can be expressed in two simple words: building standards. I would say "building codes," except that Iran, like most countries, has plenty of these, and they're not so terribly different from ours. The problem is simply that the codes have not been followed—fully 80 percent of Bam's buildings were in violation, and promptly collapsed. Corruption may be partly responsible for this sad state of affairs, but poverty and tradition are equally to blame. Throughout history, people everywhere have built their homes from locally available materials, and the poor invariably use whatever's cheapest. And there is nothing on Earth cheaper than a mud-straw brick.

Any enterprising homeowner can make these in a backyard workshop, using the yard itself for raw material and natural sunlight and muscle power as energy sources. Mud-straw bricks are fireproof and environmentally friendly, and the recipe for making them is as old as civilization itself, and can be found in any Bible, Talmud or Koran. Indeed, many humanitarian organizations have encouraged the use of mud, straw and adobe as empowering and aesthetically pleasing alternatives to modern shantytowns.

By comparison it's quite expensive to build with wood, and the process of firing clay bricks in wood-burning furnaces, or forming cement using disposable wooden molds, is even pricier. The refinement of metal and glass requires still higher energies, so it doesn't take a huge stretch of the brain to see why mud-straw bricks remain popular throughout the third world. Unfortunately, while other materials bend and groan and crack before they break—offering "soft failure modes" to ease the damage—mud bricks simply explode into powder. Thus, even buildings with a wooden skeleton will readily collapse, crushing or smothering the people inside.

Since Iran's capital, Tehran, is similarly constructed and resides directly on top of a major fault line, the Bam earthquake has stirred up a great deal of concern for the country's future. Even when funds are scarce, there are better and worse ways to build, and better and worse sites for new construction. With any luck, other small countries will take note as well, and building standards will improve worldwide. But even if the new standards are implemented without delay, it will be generations before the cities themselves are substantially safer. Is there anything we can do in the meantime? Happily, the answer appears to be yes.

A cattle call could potentially save lives

Bringing together talents in seismology, chaos theory, pattern recognition, statistics and "public safety" (a branch of civil engineering), an international team headed by UCLA geologist Keilis Borok is going after the seismological holy grail: earthquake prediction. The Earth is always shuddering and quivering as its rocky skin expands and settles against a molten interior, and Borok's plan is simply to analyze these microtremors, along with other data, for characteristics that occur only and always before a serious earthquake.

This by itself is hardly a new idea. Many people insist that "the cows are the first to know," and before an earthquake there may very well be subsonic groaning and cracking—inaudible to human ears but loud enough to terrify larger mammals. Alternatively, thanks to the piezoelectric effect from which phonograph needles used to draw their juice, squeezed rocks may give rise to electrical fields that the animals can sense. Or maybe the cows aren't the first to know, and these rumors say more about human nature than they do about earthquakes.

In any case, the first seismometer was invented in China in 132 A.D. by a craftsman named Zhang Heng, and ever since that time scientists have watched these instruments with a weatherman's eye, hoping to catch a glimpse of the future. Serious earthquake prediction programs have been longstanding features in Russia, Europe, Japan and the United States. But with its large population, traditional architecture and Pacific-Rim volcanism, China is home to 5 of the 10 deadliest earthquakes in history (including a 1556 Richter 8 that killed 830,000 people) and has worked hard to become the world leader in seismological prognostication. They have called out five distinct earthquake precursor stages: (1) changes in ground wave velocity, (2) ground tilting, (3) increased radon gas emission, (4) changes in electrical conductivity as water is squeezed in and out of the rocks and (5) characteristic foreshock patterns.

Chinese scientists used these methods successfully in 1975 to predict a Richter 7.5 temblor near the northern coastal city of Haicheng. The people were warned to sleep outside, and as a result the death toll was "only" 1,328. Possibly as many as 100,000 lives were saved.

Unfortunately, in 1976 the same Chinese authorities spectacularly failed to predict a magnitude 7.8 earthquake in Tangshan, which leveled several cities and wrought an appalling toll of 250,000 to 500,000 human lives. Since then, the Chinese have been trigger-happy, and have called out a number of false positives. And herein lies the problem, which might profitably be called "cry-wolf syndrome." Since no one will believe a seismologist who's been wrong more than twice, any prediction method had better have a low percentage of false alarms and nasty surprises.

Still, UCLA proudly notes that Keilis Borok's team predicted in June 2003 that an earthquake of magnitude 6.4 or higher would strike within nine months in a 310-mile region of central California. The Paso Robles quake occurred six months later, in the southern portion of the zone they defined. Moreover, in July they predicted an earthquake in Japan of magnitude 7 or higher by Dec. 28, in a region that includes the northern island of Hokkaido. A magnitude 8.1 earthquake struck Hokkaido on Sept. 25. The team's latest prediction is that a temblor of Richter 6.4 or higher will occur in the southeast Mojave desert sometime before Sept. 5th, 2004. If this turns out to be correct, then UCLA may soon raise their banner as the world's number-one quake prediction center.

Save the Earth by blowing it up

Simply identifying the danger zones is a long way from pinpointing the exact epicenter and time of failure, but our instruments and analytical methods are improving year by year. GPS has provided a bonanza of ground movement data, while satellites can increasingly track moving bulges and subsurface density anomalies. It isn't hard to imagine a future where particular bits of doomed, stressed-out rock can be identified beneath the crust, months or years before they actually break. With this information in hand, residents can choose to evacuate or ride it out, just as we do today with hurricanes and fires.

But if we have this much information, how hard would it be to drill a deep hole (a "mohole" in geological lingo), and drop in a small H-bomb of our own? Heaven knows we've got enough H-bombs lying around, and since the Earth's interior is radioactive anyway, there's no real danger of contaminating anything. By setting off a small explosion early, to avoid a much larger one later, we may send unplanned earthquakes straight to history's rubbish bin. Think "controlled burn."

But hey, there'll always be a constituency out there that objects, on general principle, to any tampering with the primal forces of nature. That's their prerogative, and if the nays outnumber the yeas, then we may just have to let the Earth shake us when and where she pleases. But with the latest crop of designer materials entering the architectural marketplace, this may not matter very much.

Earthquakes may no longer rock the house

The Denver International Airport was built with $5 billion of Colorado taxpayers' money, but the main terminal building owes its architectural heritage to that primal eldest human structure, the tent. DIA's roof of Teflon-coated Kevlar fabric has survived two major blizzards and any number of windstorms, and if it did somehow collapse I have a hard time imagining it would really hurt anyone. In fact, the building's stylish look is being copied all over Denver, in stadiums and bus stops and streetside kiosks. It's fast becoming a part of the city's signature style, but not for any highfalutin' notions of aesthetics or public safety. In fact, in a land of high wind and unpredictable snow, it's simply cheaper in the long run than any of the alternatives.

Similarly, new materials like carbon fiber and foamed aluminum offer lightweight, high-strength, low-cost alternatives to wood and steel and cement. And with both artificial diamond and superstrong carbon nanotubes scheduled to enter commercial mass production this year, we may soon see materials with 600 times the strength-to-weight ratio of steel, at a price that's competitive with high-quality lumber. In all fairness, diamond is a flammable material that releases tremendous heat if you can manage to ignite it. But this is very difficult to do, and in fact all metals are flammable in exactly the same way. It's just that the ordinary heat of, say, burning gasoline is insufficient to ignite most of them.

So we may yet see a day when Americans, like Third-Worlders, build our dwellings from the cheapest available materials, the only difference being that these bargain-basement building blocks will not shatter in a minor quake, or even a major one, and will in fact be impervious to any conventional harm, from tornadoes to fires to the sudden sharp impact of a crashing airplane. Your house may fall over, but it will never fall apart. And if that day comes, why, we may look back and wonder why anyone, anywhere, was ever killed by a mere Richter 9.