The report suggested four 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. The early Los Angeles oil boom began in 1892 with discovery of petroleum near the site of the present-day Dodger Stadium. By 1923 drilling in the L.A. basin accounted for nearly 20 percent of the world's total production of crude. "It's possible it was just an early 20th century phenomenon," Hough said of the flurry of quakes she studied. "Maybe the LA basin as a geological unit is more seismically stable than we've estimated."

Source: Otago Daily Times November 02, 2016 03:41 UTC