We already know that in recent years, disposal of waste water from the fracking process in oil and gas fields has caused recent small earthquakes in Oklahoma and elsewhere, to the extent that the U.S. Geological Survey now factors it into its maps of seismic risks.
Now a new study suggests the connection between energy production and quakes may go back a long time - to the early 20th Century, when drilling in the Los Angeles area possibly may have induced four historic earthquakes between 1920 and 1935.
The researchers uncovered evidence in historical records indicating that the 1920 4.9 magnitude Inglewood quake, the 1929 4.7 Whittier quake, the 1930 5.2 Santa Monica quake and the 6.4 quake that occurred off Long Beach in 1933 may have been induced by oil production activities that took place prior to the time of the seismic events.
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Early oil drilling methods were different than those used today, and the study doesn't indicate any heightened earthquake risk from the drilling that still goes on in the area.
"With the advent of water flooding and other changes in industry practices, you may not find these kinds of induced earthquakes after 1935," USGS scientist Susan Hough, said in a press release. "It's possible it was just an early 20th century phenomenon." She and USGS colleague Morgan Page worked on the study.
The findings, in a study to be published Nov. 1 in Bulletin of the Seismological Society of America, also are a reminder of a time when California could claim to be the oil capital of the world. In fact, the state still ranks among the top oil-producing states in the nation.
According to a state government history of the California oil industry, oil extraction in the Los Angeles area dates back as far as 1856, when a San Francisco-based company began working at the La Brea tar pits.
In 1892, Edward Doheny and partner Charles Canfield used pickaxes to dig a well near what is now the corner of Glendale Boulevard and Colton Street, a short distance to the southwest of what is the present-day location of Dodger Stadium. Their 200-foot-deep shaft produced just 10 gallons a day at first, but it attracted the attention of other oil outfits, who drilled deeper, according to a 2012 Los Angeles Times retrospective.
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The industry grew rapidly. By 1895, the Los Angeles field was producing 750,000 barrels annually, about half of the state's output. Another early oil driller in Los Angeles was Edward A. Clampitt, whom the Times reported may have been the inspiration for Jed Clampett in the 1960s sitcom "The Beverly Hillbillies."
Over the next several decades, the oil boom helped turn Los Angeles from a small city of 50,000 into a major metropolis with a population of 1.2 million. According to a 2014 Atlantic article on the region's oil past, by 1930, Los Angeles accounted for a quarter of the entire world's oil production.
But the oil may have come at a cost, if the connection suggested by the new study is borne out. The 1933 Long Beach quake leveled buildings and killed 115 people, in addition to causing $40 million in property damage. The catastrophe led to passage of legislation in California that required buildings to be built to withstand quakes.
Though Los Angeles is better known today for the movies and television shows made there, the oil industry remains productive, with 55 active fields and 3,700 derricks still operating throughout the area. But oil isn't as obvious because the infrastructure has been concealed to blend in with the urban landscape.
One installation is housed in a fake office tower on Pico Boulevard. In the waters off the satellite city of Long Beach, for example, oil derricks are disguised as ersatz islands with palm trees. There's also an active oil field near Cedars Sinai hospital and the Beverly Center shopping mall.
California still ranks third in crude oil production in the nation, but its output was less than a fifth of production in Texas and about half of what North Dakota drilled in July 2016, the most recent month for which data was available from the U.S. Energy Information Administration.
Photo: The oil field at Signal Hill in the Los Angeles Basin in 1923. Credit: The Aerograph Co./ US Library of Congress