The Seismic Rehabilitation of Historic Buildings
Source: National Park Service, Preservation Brief #41
Earthquakes result from sudden movements of the geological plates that form the earth’s crust, generally along cracks or fractures known as “faults.” When buildings are not designed and constructed to withstand these unpredictable and often violent ground motions, major structural damage, or outright collapse, can result, with grave risk to human life. Historic buildings are especially vulnerable to seismic events, particularly those built before seismic codes were adopted. Also, more and more communities continue to adopt higher standards for seismic retrofit of existing buildings. And, despite popular misconceptions, the risks of earthquakes are not limited to the West Coast, but exist across much of the United States.
Although historic and other older buildings can be retrofitted to survive earthquakes, the process of doing so may damage or destroy the very features that make such buildings significant. While life-safety issues remain foremost concerns, fortunately, there are various approaches which can help protect historic buildings from both the devastation caused by earthquakes and from the damage inflicted by well-intentioned, but insensitive, retrofit procedures. Building owners, managers, consultants, and communities need to be actively involved in planning for and readying irreplaceable historic resources from these threats.
This Preservation Brief provides information on how earthquakes affect historic buildings, how a historic preservation ethic can guide responsible retrofit decisions, and how various methods of seismic rehabilitation can protect human lives and historic structures. The Brief provides a description of the most common vulnerabilities of various building construction types and the seismic strengthening methods most often needed to remedy them. A glossary of technical terms is also provided at the end of the Brief.