A building may be tough enough to endure many sorts of natural and man-made calamities, but that doesn't necessarily mean it will be able to withstand an earthquake. Earthquakes generate the same sorts of forces as other disasters, but they do it differently — in ways that a building's structure may not be designed to endure.

Both a hurricane and an earthquake, for example, subject a building to lateral and vertical forces, but not in the same fashion. The storm will threaten to blow the building off the ground by pushing against it and lifting it upwards, creating a whiplash effect that may cause the structure to break. During a quake, it's the ground that moves, while the building resists the shaking. Although most of the ground movement usually is horizontal, a quake can also rock a building up and down, like a rodeo rider on an angry bull.

Nevertheless, architects and engineers say it is possible to design and erect buildings that can survive a major quake — and to retrofit older buildings so they can better cope with a quake's destructive forces.

Erecting a new quake-proof skyscraper may only add a few percentage points to the cost, but fixing older buildings can be far more expensive; the California Seismic Safety Commission's plan to quake-proof all California buildings by the year 2020, for example, could cost in the tens of billions of dollars. And as the Kobe earthquake demonstrated, where builders choose to build is one of the most crucial factors. Solid rock or coherent soil strata are the best locations from a safety standpoint. Even a relatively well-designed building on soft, damp soil or manmade fill may be in big trouble during a quake, as tremors cause the ground beneath it to turn temporarily from solid to liquid.

There are two schools of thought on how to use the foundation to quake-proof a building. One method is to tie the foundation to the superstructure — the upper part of the building — as solidly as possible. That way, when the ground shakes, the two pieces may move as a unit, instead of having the upper floors topple. An alternative strategy is to design the superstructure to move atop the foundation, so that despite the shaking beneath it, the building will remain in one place.

Again, there's more than one way to do it. One approach is to make a building as big and stiff as possible, with no weak spots, so that it'll withstand a quake and stay in one piece. The converse is to deliberately design parts of the frame to move, so that in the event of a quake, the frame will deform slightly and absorb the shaking without losing its integrity.

Many quake victims are struck by masonry, window frames and metal pieces that rain down from shaking buildings. That's why state-of-the-art quakeproofing calls for designing these elements to stay in place when the ground starts to move.

Buildings vibrate at different frequencies during a quake. A one-story house may have a period of 0.1 seconds, but a multi-story building may hit 0.5 seconds, and 10-20 story office tower may vibrate at 1 to 2 seconds. That's worrisome because soil has a frequency range that's perilously close (0.5 to 1 second). If the ground beneath a building vibrates at the same rate as the structure itself, the two achieve a state called resonance, which will intensify the quake's effect on the structure, quite possibly, causing it to fail. That's why it's crucial for builders to calculate the two values and if necessary, stiffen a building to make sure they don't match.

Even if they survive a quake's forces, buildings face the threat of blazes that inevitably erupt in the tremors? wake. San Francisco learned that lesson in 1906. Today, the city is protected by a special auxiliary water system, run by the fire department, which includes a million-gallon reservoir and 100 miles of quake-resistant pipes connected to high-pressure fire hydrants. If the reservoir runs out, the system can draw more water from the San Francisco Bay.

Unlike hurricanes, which can be predicted with enough precision that people can be evacuated before they reach land, earthquakes hit with no warning. In various earthquake-prone locales, Russian, Japanese and American scientists are doing research they hope will change that. U.S. efforts are focused upon Parkfield, California, a town along the San Andreas fault where 6.0 earthquakes strike on the average every 22 years. Researchers have installed an array of sensitive equipment, in an attempt to discover phenomena that might give warning of an impending quake. A similar project is underway in Kobe, Japan, where researchers are hoping to discover whether rocks under stress emit electromagnetic signals in the weeks before a quake.

The Richter Scale, developed by CalTech scientist Charles Richter in the 1930s, quantifies how much the ground shifts during a quake. The Richter scale is logarithmic; each one-point increase represents a ten-fold jump in the amplitude of an earthquake's seismic waves, and a 30-fold increase in the amount of energy released. A 7.0 quake, for example, has many times the destructive energy of a 6.0. A 2 or 3-magnitude quake is big enough to be felt by people, and generally quakes have to be at least 5.0 to cause damage. 6.0 or higher is considered a major earthquake, and quakes of 7 or higher can cause loss of life and property on a catastrophic level. The only earthquake in the 20th Century to reach or exceed 9 on the Richter Scale was the May 1960 earthquake in Chile, which registered 9.5. The greatest loss of life came, however, from the 8.2 quake which struck China in July 1976, killing nearly 250,000 people.