By Elke Weesjes
Long Beach Earthquake 1933
EARTHQUAKES CAUSED BY oil and gas drilling in Oklahoma and other states are causing a stir these days. But they’re not a new phenomenon.
More than a dozen disastrous earthquakes in the Los Angeles area in the early 20th century may have been induced by oil production activities, according to a new study by Susan Hough and Morgan Page of the U.S. Geological Survey. Their findings are especially important because they will likely reshape how seismologists calculate the rate of natural earthquake activity in the Los Angeles basin.
A Wild West industry
The oil boom in Los Angeles began in 1892 when an oil field, about four miles long and a quarter mile wide, was discovered in the city’s Elysian Park neighborhood near the present-day Dodger Stadium. This field is only one of many in the Los Angeles Basin. Others include the Salt Lake and Beverly Hills fields, the Los Angeles Downtown, the Brea-Olinda field, and the Huntington Beach field.
By 1923, these oil fields in the Los Angeles Basin accounted for nearly 20 percent of the world’s total production of crude oil (Gorman, 2016). However, retrieval methods to get the oil out of the ground weren’t as evolved as they are today, according to Hough.
“It was kind of more of a Wild West industry back a hundred years ago, and the technology wasn’t as sophisticated, she told the Los Angeles Times. “People would just pump oil, and in some cases the ground would subside—fairly dramatically” (Rong-Gong Lin II).
In their study, which was published in November in the Bulletin of the Seismological Society of America, Hough and Page reviewed state oil drilling reports from the time. The researchers compared industry data, such as drilling permit approvals and well abandonments, to a list of the 22 biggest earthquakes in the period 1900-1935. They found links between earthquakes, including the 1920 Inglewood earthquake, the 1929 Whittier quake, and the 1933 Long Beach quake, and nearby oil productions activities that took place around the same time as the tremors occurred (Hough and Page, 2016).
Long Beach 1933
Of the 13 earthquakes that were likely caused by oil production activities, the 6.4-magnitude tremblor that shook Long Beach in 1933 was especially devastating. Between 115 and 120 people died and property damage topped $40 million (which would amount to $722 million today).
The authors discovered that this deadly tremblor occurred less than nine months after directional drilling1 in the Huntington Beach oil field—the location of the earthquake’s epicenter—first extended into offshore tideland reserves, reaching depths of over 8,000 feet (Hough and Page, 2016).
Hough and Page observed something similar before the 1929 Whittier quake. This 4.7-magnitude tremblor occurred about five months after the initial exploitation of production horizons at depths below 6,000 feet.
Long Beach Earthquake 1933
“And again, if you look at where the production was concentrated … it was essentially smack on top of where the earthquake was centered,” Hough told the Los Angeles Times (Rong-Gong Lin II).
Since the timing of most of the earthquakes they studied correspond with times when wells were being significantly deepened, the authors believe that the depth of wells is a key factor. After all, drilling deeper means getting closer to the basement rock, and thus closer to the tectonically active faults (Phys.org, 2016).
In the period after the Long Beach earthquake, drilling methods changed dramatically, which might explain why a study by Hauksson et al. (2015) concluded that there was no significant evidence for induced earthquakes in the Los Angeles area since 1935.
"With the advent of water flooding2 and other changes in industry practices, you may not find these kinds of induced earthquakes after 1935," Hough told Phys.org. "It's possible it was just an early 20th century phenomenon"(Phys.org, 2016).
Maybe the L.A. basin as a geological unit is more seismically stable than we’ve estimated
Throughout their study, the authors emphasize that the link between oil extraction and seismic events in the Los Angeles basin does not apply to modern extraction practices, namely hydraulic fracturing, or fracking. Still, their findings are relevant today because they suggest the natural rate of earthquake occurrences in this area may be significantly lower than previously calculated.
“Maybe the L.A. basin as a geological unit is more seismically stable than we’ve estimated,” Hough told Reuters.
Gorman, Steve. 2016. “Early Los Angeles-area quakes linked with oil production” Reuters, November 1, 2016. http://uk.reuters.com/article/us-california-earthquakes-study-idUKKBN12W53T (accessed on December 7, 2016).
Hauksson, E., T. Gobel, J.‐P. Ampuero, and E. Cochran. 2015. “A century of oil‐field operations and earthquakes” The Leading Edge, June, 2015.
Hough, Susan E. and Morgan Page. 2016. “Potentially Induced Earthquakes during the Early Twentieth Century in the Los Angeles Basin” Bulletin of the Seismological Society of America, November 1, 2016. http://bssa.geoscienceworld.org/content/early/2016/10/27/0120160157.full (accessed on December 7, 2016).
Phys.org. 2016. “Some Los Angeles Earthquakes possibly triggered by oil production in early 20th century. Phys.org, October 31, 2016. http://phys.org/news/2016-10-los-angeles-earthquakes-possibly-triggered.html.
Rong-Gong Lin II. 2016. “Southern California’s deadliest quake may have been caused by oil drilling, study says” Los Angeles Times, October 21, 2016. http://www.latimes.com/local/la-me-ln-oil-drilling-earthquake-20161031-story.html (accessed on December 7, 2016).