Study: Drilling may have caused deadly 1933 California quake

Associated Press

LOS ANGELES

New research suggests oil drilling decades ago may have triggered earthquakes in the Los Angeles region, including the 1933 quake that killed more than 100 people.

If confirmed, it would be the first time oil operations have been linked to a deadly quake in the U.S.

Scientists from the U.S. Geological Survey combed through records and identified several quakes in the 1920s and 1930s that were potentially caused by industry activities, including the 1933 magnitude 6.4 jolt that struck the city of Long Beach.

Until now, “we pretty much assumed that earthquakes in the LA area are natural and that induced earthquakes are either not happening or not significant,” said USGS seismologist Sue Hough, who led the study.

Drilling techniques have changed through the decades, so the findings don’t necessarily point to a current risk. A separate study last year by a team at USGS and California Institute of Technology found no significant evidence of human-caused quakes in the LA region after 1935.

Man-made quakes have been in the spotlight after a sharp uptick in seismic activity in Oklahoma and Texas. Studies have linked the spike to the practice of injecting leftover wastewater into the ground after drilling for oil and gas using newer technologies such as hydraulic fracturing.

Hough and colleague Morgan Page pieced together a list of quakes between 1915 and the early 1930s, and reviewed oil permits and drilling operations during that time period. They found 13 cases of shaking that may have been caused by oil production ramping up.