Preliminary Geologic Map of the Los Angeles 30' x 60' Quadrangle, Southern California

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.

[Summary provided by the USGS.]