05/06/2002

THE CENTURY-OLD Rhode Island State House stands proudly on the edge of downtown as a symbol of the state's strength and perseverance. It is also one of the most beautiful structures in the state, one that links us to our past.

But this formidable building, like so many of our older landmarks, would almost surely be damaged were a significant earthquake to hit the area. While we Easterners often imagine that earthquakes are only a problem for the West Coast, Rhode Island actually had a small tremor in March, and more recently felt tremors from a substantial earthquake in upstate New York.

Although the risk is slight that a significant earthquake will strike New England in the near future, it would be wise to consider now how best to protect ourselves, and our architectural heritage, against the possibility.

It is difficult to know just how distinct that possibility is. When earthquakes strike out west, we often hear experts talk about the fault line connected to the tremor. They can monitor the fault and actually see it break and offset the ground surface during an earthquake.

We have several fault lines here in New England, but, according to the U.S. Geological Survey, earthquake locations cannot be measured as accurately east of the Rockies because the fault lines do not break the ground surface. Thus, we cannot base predictions about future quakes on the location of fault lines alone.

In fact, there is no reliable way to know where or when the next damaging earthquake will occur.

If we decide that certain older buildings, such as the State House and some of our older churches and other historic buildings, not to mention schools, hospitals, power plants and the like, should be given an extra measure of protection against earthquakes, retrofitting is the only real option. This entails installing steel rods or other structural improvements that will better withstand any stresses put on the building.

This is expensive, but certainly less expensive than repairing a structure damaged or destroyed by an earthquake. California law requires that certain buildings be retrofitted to protect older buildings and the people inside them. We on the East Coast unfortunately do not have that kind of protection.

Why, exactly, are older buildings so vulnerable to earthquakes? The problem lies in the materials used. Most older buildings were constructed primarily of bricks and mortar. While this is durable matter, it is not capable of withstanding the stress caused by vibration in an earthquake.

In the past, when almost all large buildings were constructed with these materials, large earthquakes ravaged such cities as Charleston, S.C., and San Francisco. To avoid such catastrophes, we need to retrofit to strengthen the building by incorporating less brittle material into structures.

Newer buildings, of course, can much more easily be made to withstand the stress of tremors and other forces that act upon them. In fact, the building code of most states requires that this be done, specifically with earthquakes in mind. New information is constantly being gathered that lets engineers improve these codes and their structural designs.

Current design possibilities let buildings to escape minor damage during slight ground-shaking, which happens more often than most people realize, and also remain standing even during severe earthquakes.

Rhode Islanders are fortunate to live in an area where earthquakes are infrequent. However, we should not be so complacent as to think that one might never affect us. It would be wise for us to consider how best to protect our state's historical landmarks in the event of a major earthquake, and it would be foolish not to ensure that every new building can withstand whatever natural disaster might occur.

Bruce L. Davey is a structural engineer.