The Los Angeles 30' x 60' quadrangle covers approximately 5,000 km² including much of the densely populated urban and suburban areas of the southern California megalopolis. The quadrangle is about 90 km east-west and about 55 km north-south, extending from Fillmore and Thousand Oaks in the west to Vincent in the northeast and Montebello in the southeast. It covers the urban San Gabriel Valley and San Gabriel Mountain foothill communities from Monrovia to Pasadena, as well as Glendale, downtown Los Angeles, Hollywood, Santa Monica, Malibu, and all the communities in the San Fernando Valley, Simi Valley, and the upper Santa Clara River Valley. Population of these urban and suburban areas, as listed in the 2000 Census, totals approximately 5.6 million, and property value is estimated to total hundreds of billions of dollars. The quadrangle also includes large areas of wilderness in the Angeles and Los Padres National Forests, in the Santa Monica Mountains National Recreation Area, and the Sespe Condor Sanctuary. The relief in the quadrangle ranges from about a hundred meters sub sea (in Santa Monica Bay) to more than 2,000 meters above sea level at Pacifico Mountain in the high San Gabriel Mountains. Residents and transient visitors are subject to potential hazards from earthquakes, debris flows and other landslides, floods, wildfires, subsidence from ground water and petroleum withdrawal,

This geologic map is intended to illustrate the distribution of the rocks and surficial deposits of the area and their structural and stratigraphic relations to one another. It provides a regional geologic framework as an aid to better evaluations of the potential for hazard from active earth processes; however, it is not sufficiently detailed to serve as a basis for site-specific evaluations.