U.S. Geological Survey Scientists in Pasadena Say 1933 Long Beach Earthquake May Have Been Caused by Oil Drilling

Deep oil drilling on Huntington Beach in the Los Angeles basin could have caused the 1933 Long Beach earthquake, the deadliest earthquake ever to hit southern California on record, a new study by two government scientists in Pasadena suggests.

A report in the Los Angeles Times Monday said the study, written by scientists Susan Hough and Morgan Page at the U.S. Geological Survey field office in Pasadena, will be published in the Bulletin of the Seismological Society of America on Tuesday.

The study also suggests that three other earthquakes, including magnitude 5.0 earthquakes in Inglewood in 1920 and in Whittier in 1929, may also be linked to oil drilling.

The 1933 quake, recorded with a 6.4 magnitude, killed between 115 and 120 people and toppled hundreds of buildings in the area.
Hough and Page wrote the report after combing through old California oil drilling records.

According to the LA Times, the two scientists discovered that some of the Los Angeles Basin’s largest earthquakes between 1900 and 1935 happened shortly after significant changes were made in oil production in nearby fields. At the time, the Los Angeles area was one of the world’s leading oil producers.

“It was kind of more of a Wild West industry back a hundred years ago, and the technology wasn’t as sophisticated,” Hough tells the LA Times. “People would just pump oil and in some cases the ground would subside – fairly dramatically.”

Drilling for oil could have changed stresses on underground rock, and that could have pushed earthquake faults to rupture, the study said.

The report’s finding does not mean that oil drilling is causing earthquakes in Southern California today. Other scientists have looked at earthquakes during more recent decades and have not found any reason to blame oil production for triggering earthquakes more recently in the L.A. Basin, said the report.

Last year, Hough and Page also published a study pointing to oil production activities that could have induced most of the significant earthquakes in Oklahoma during the 20th century.

The Long Beach earthquake was so called because the worst damage occurred in that city, but the epicenter of the earthquake was actually in the Huntington Beach area. The quake destroyed many brick buildings, and prompted officials to ban new construction of weakly reinforced brick buildings.

Among the sources Hough and Page studied were state reports on oil field operations that precisely identified where drilling had happened. Hough said she found that there was notable drilling activity very close to the epicenter of the Long Beach earthquake that had begun just nine months before the temblor.

The LA Times said the scientists identified five earthquakes in Southern California between 1900 and 1933 that were magnitude 5 and above. One was offshore west of Santa Monica, and there was no evidence it was linked with oil production. But for the other four earthquakes – in 1920, 1929, 1930 and 1933 – in each case, the epicenter was no more than a few miles away from where there was notable oil drilling in the three to nine months before the earth shook.

If the report proves to be true, one promising implication would be that the L.A. Basin is not as naturally seismically active as it is believed to be. Geologically, the area could be safer than previously thought.

However, it could also mean that human-induced earthquakes, like the 1933 could possibly be, could cause more damaging earthquakes than some previously thought were possible.

One thing that’s certain, the scientists tell the LA Times, is that nothing in the study suggests that a halt to oil drilling would stop earthquakes from happening in Southern California. The state sits on the edge of two gigantic tectonic plates that create strain as they move past each other, and that strain must be released through earthquakes.