N.Y. Girds for Quake, Through Fault of Its Own

THE Big Apple has had plenty of political earthquakes over the years. Now, it's getting ready for the real thing - where the earth shakes, buildings sway, and fault lines add new character to the landscape.

New construction in the city will have to have greater resistance to earthquakes. The new standards, approved by the New York City Council last week, will require such changes as better soil studies, tighter regulations for building on landfill, and consideration of the effect of the vibration of adjacent buildings.

New construction will require reinforced masonry and stronger standards for steel and reinforced concrete. The standards, however, are not as tough as those in California.

Although New York does not have the tectonic activity of California, Empire State earthquakes do occur. In 1984, a 4.0-magnitude quake shook the Westchester town of Ardsley. And in 1884 there was an earthquake of 5.0 about 15 miles off Coney Island.

Unlike California, where two plates meet and strains build up, New York is in the middle of a geologic plate. Thus the strains here are less. New York does not have a truly major fault, but ``has many faults,'' says John Armbruster, a seismologist at Columbia University's Lamont-Doherty Earth Observatory in Palisades, N.Y.

Some of the faults in New York, however, are observable. For example, there is a fault line that creates a valley across Manhattan's 125th Street.

During the construction of a new water tunnel, geologists went into the tunnel to look at the shifting rocks. ``They saw rocks on two sides that looked very different,'' Mr. Armbruster says.

Although geologists have a limited record of earthquakes in New York, they appear to happen about every 100 years. Since the last quake was 110 years ago, ``New Yorkers should not be surprised if they have one,'' adds Armbruster.

New York has suffered only minor damage so far from temblors. The 1884 quake toppled brick chimneys, shattered windows, and caused some panic. Fortunately, there were no fatalities.

Should another earthquake of the same magnitude, or higher, rattle the city, the Big Apple might not be so fortunate. Archie Spigner, sponsor of the city council measure, estimates that another earthquake that measured 5.0 would cause $25 billion in damage today. The possibility of an earthquake ``cannot be ruled out,'' he told council members.

The city's new rules will also put it into compliance with revised federal standards, says Anthony Baronci, the legal counsel for the city council's infrastructure division.

All new federal buildings as well as structures receiving federal Housing and Urban Development mortgages or grants must be in compliance with federal standards to qualify. ``We don't want to jeopardize federal money,'' says Mr. Baronci.

The real estate industry supports the rules, although they will add 2 to 5 percent to construction costs.

``It's accepted as part of the cost of promoting public safety and guarding against a peril we hope will never arise,'' says Warren Wechsler, a spokesman for the New York State Real Estate Board, an industry group.

Many of the city's skyscrapers already meet strict standards because they are designed to sway during hurricane-force winds. Such flexibility tends to protect buildings during earthquakes.

New York's venerable brownstones, however, are built of unreinforced masonry. They would be vulnerable in a quake. In addition, scores of buildings, including those at John F. Kennedy International Airport, are sited on landfill.

In other earthquakes, landfill has liquefied - practically turning into jelly - resulting in substantial damage. This happened extensively in Kobe, Japan. New York will now take this into account.