A magnitude-7. 5 earthquake occurring along the central portion of the Wasatch Fault, Utah, may cause significant damage to Salt Lake County's domestic water system. This system is composed of water treatment plants, aqueducts, distribution mains, and other facilities that are vulnerable to ground shaking, liquefaction, fault movement, and slope failures. Recent investigations into surface faulting, landslide potential, and earthquake intensity provide basic data for evaluating the potential earthquake hazards to water-distribution systems in the event of a large earthquake. Water supply system components may be vulnerable to one or more earthquake-related effects, depending on site geology and topography. Case studies of water-system damage by recent large earthquakes in Utah and in other regions of the United States offer valuable insights in evaluating water system vulnerability to earthquakes.