Many of the most damaging earthquakes in Southern California over the last 100 years may have been the result of oil industry activity the area, according to new research from the US Geological Survey.
The new findings relate to common oil industry practices of the time, it should be noted, which are rather different than those of today. Importantly, the research suggests that the “natural” rate of earthquake occurrence in the region may be lower than originally thought.
In a paper on the subject, the researchers involved — Susan Hough and Morgan Page of the US Geological Survey — make a clear distinction between their findings and those concerning the recent linking of wastewater injection wells and earthquakes in Oklahoma. The techniques and technologies used in the two circumstances/times are notably different.
The researchers stated that the findings “do not necessarily imply a high likelihood of induced earthquakes at the present time.”
The Guardian provides more: “The report suggested 4 major Los Angeles-area quakes in 1920, 1929, 1930, and 1933 were triggered by early drilling methods in which oil was extracted without water being pumped into the ground to replace it, causing the ground to subside. This could have artificially placed more pressure on seismic faults near oilfields. The most devastating event was the so-called Long Beach earthquake of 10 March 1933, a 6.4-magnitude quake that ruptured the Newport-Inglewood fault along the coast, toppling scores of buildings and killing 115 to 120 people — the highest death toll on record from a southern California earthquake.”
The only earthquake in Californian history (that’s the state’s history, not the local land’s history) to have been more damaging or deadly was the infamous Great San Francisco earthquake of 1906. That earthquake reduced much of the city to rubble, set off numerous fires, and killed at least 3,000 people (a very large proportion of the city’s population at the time).
As some background, the oil boom in the Los Angeles area began in 1892, following the discovery of a field near the current Dodger Stadium. Once in full swing by 1923, the Los Angeles Basin was responsible for around 20% of world crude oil production.
“It’s possible it was just an early 20th century phenomenon,” stated researcher Hough. “Maybe the LA basin as a geological unit is more seismically stable than we’ve estimated.”
The new research is detailed in a paper published in the Bulletin of the Seismological Society of America.
Image by W.L. HUBER, USGS