As a consequence of the Northridge earthquake, the Los Angeles Division of Water and Power (LADWP) water delivery system required repairs at over 1,000 locations. A Cornell University research team at the Multidisciplinary Center for Earthquake Engineering Research headquartered at the University of Buffalo (EEC-9701471), led by Professor Thomas O’Rourke and including graduate and undergraduate students, collected data on nearly 1,100 repair sites and digitized about 11,000 km of distribution mains and 1,000 km of trunk lines. This became the foundation for the largest geographic information system (GIS) database on lifeline seismic performance ever assembled in the US. In addition to assistance from LADWP, key information and data on pipeline characteristics, and pre and post event system surveys using Global Positioning System control points were contributed by the Southern California Metropolitan Water District, CalTrans, and the Los Angeles Bureau of Engineering. The relational database was further enhanced by addition of more than 240 corrected strong ground motion records, vectors of earthquake induced horizontal displacement, heave and settlement, surficial soils distribution and depths to water table. The outcome is a rich characterization of the world beneath Angelenos’ feet, and is being used as a template for modeling water supply losses in other US urban areas through incorporation in ASCE prestandards and FEMA’s HAZUS loss estimation methodology.