- © 2007 Association of Engineering Geologists
The City of Los Angeles is located on the east edge of the Pacific Plate, within the wide transform boundary zone with the North American Plate and near the big bend in the San Andreas fault. Situated just south of this restraining bend, the city is within the Western Transverse Ranges which are undergoing transpressional uplift along active thrust faults. The city has experienced and mitigated the effects of earthquakes on the San Andreas and local faults, floods, fires, droughts, landslides and debris flows.
The natural resources of Los Angeles include vast oil and gas deposits and the La Brea Tar Pits, an important Pleistocene fossil locality. Urbanization over and tunneling through both abandoned and active oil and gas fields have encountered hazardous conditions. Seepage of hazardous gasses has caused explosions within the city and as a result Los Angeles established methane mitigation requirements for construction in methane hazard zones.
Los Angeles has been aggressive in addressing issues of air, soil and water pollution control. A master plan for solid waste management has been implemented, regulating the siting and operation of landfills. Local sources of drinking water are inadequate to support the population. Importation of drinking water via three aqueducts has fueled the city's growth and agricultural prosperity.
The practice of engineering and environmental geology has been greatly influenced by laws, practices and policies that were started in or influenced by the City of Los Angeles. These include the 1915 Los Angeles Flood Control Act, 1929 California Dam Safety Act, 1958 Engineering Geologists Qualifications Board, 1933 Field Act, 1972 Alquist-Priolo Act, 1975 Seismic Safety Act, 1990 Hazards Mapping Act, and modifications to the Uniform Building Code for seismic safety.
- Los Angeles
- Port of Los Angeles
- Pier 400
- Oil and Gas Deposits of Los Angeles
- La Brea Tar Pits
- Blind Thrust Fault
- Methane Hazard Mitigation
- Hazardous Waste
- Solid Waste
- Seismic Retrofit
There is much about Los Angeles that has affected the profession of engineering geology, perhaps more than any other city. The need for infrastructure was evident soon after its founding, given its agreeable climate coupled with the shortage of water; a population boom, with its consequent transportation requirements; and recurring large earthquakes amid the rumble of smaller, stress-relieving tremors. The Los Angeles area is a popular destination, and the historic development of the city recounts a story that highlights the fact that technical expertise is constantly needed to meet the challenges of urban development in an environmentally changing and tectonically active area.
Geologic surprises typically affect the daily lives of Los Angeles residents. Little was known about the geologic history of the area when the University of California at Los Angeles (UCLA) opened its campus in 1928. Engineering geologist Rollin Eckis pieced together the geologic framework of a basin and basement-complex for one of UCLA's first Ph.D. dissertations in 1932. Stratigraphers, structural geologists, and paleontologists became entranced with the sedimentary basin fill, all 30,000 ft (9,100 m) of it, and their findings were used by petroleum geologists to discover and produce huge volumes of oil. Further studies confirmed that the Los Angeles area is located over a deep sedimentary basin with hills composed of folded Miocene and Pliocene sedimentary rocks. The basin is rimmed by the crystalline rocks of the Santa Monica Mountains and the San Gabriel Mountains.
The nearby San Andreas fault and other active faults are a constant reminder of how the power of nature can affect the works of man. Each year, and with each moderate earthquake, we learn more about geologic processes and how they affect urban life in Los Angeles. Newly recognized blind thrust faults provide new challenges to our understanding of the neotectonic evolution of the Los Angeles basin. Although we know more about earthquakes and seismic effects than ever before, most Los Angeles residents still fear “the Big One,” an earthquake larger than the 1933, 1971, or 1994 events. We trust that the structural engineers have designed high-rise buildings that will ride through the “Big One” with minimal loss of life and property damage.
Engineering geology as we know it today grew from adolescence to maturity in Los Angeles, from 1950 through the advent of the environmental response era. Post–World War II hillside development and the sustained rainfall in the spring of 1952 led to major slope failures and damage to thousands of homes. As a result of these occurrences, engineering geologists were given new status and responsibilities by the city and county. Today, engineering geology and geotechnical engineering are thoroughly integrated in the Los Angeles area. High-rise and deep-basement architecture are now used as buildings are increasingly taller and basements are deeper to accommodate the ever-present automobile and its occupants. For example, foundation engineering innovations were required to design and construct these buildings, and the development of the tie-back anchor made temporary construction-retention of basement cuts possible in the weak rock that is characteristic of the region.
Los Angeles has suffered numerous environmental setbacks, but it routinely responds with aggressive regulations to mitigate the impact of these events. Air pollution control and regulation were born in Los Angeles, and much of the present hazardous waste management and remediation process grew from examples within and around this city. Los Angeles enters the 21st century with a strong effort to replace its once world-class public transportation network, killed by the post–World War II romance with the automobile, with a new Metro rail system. The city has the heart to meet and survive its urban pressures and environmental constraints, and engineering geology will play an integral role in the development of solutions to problems as they arise.
The Geology of Los Angeles has unique appeal to me as the series editor. Two of the 1781 town-founding, leather-jacketed soldiers of Spain's army were my grandfathers (seven times removed). This is my city of birth and of my early geology education (at UCLA). I am even more enthused than usual about the geologic impacts on this great center of commerce and terminus of America's historic 1847 expansion to the Pacific Ocean.
Allen W. Hatheway, Series Editor
Rolla, MO, and Big Arm, MT