Oklahoma and Kansas are fast becoming the earthquake capitals of the U.S., shaken frequently by temblors almost unknown in the 20th Century.

Repeated studies have revealed the cause: Hydraulic fracturing on shale formations to capture oil and gas trapped in the underground strata.

But it turns out that another state experienced a similar wave of man-made quakes, and a century before the current Great Plains epidemic.

From the U.S. Geological Survey:

A new study from the USGS suggests that some early 20th century earthquakes in southern California might have been induced (man-made) by past practices that were used by the oil and gas industry.

In the new study, scientists evaluated the likely cause of several significant earthquakes within the Los Angeles Basin between 1900 and 1933, together with consideration of available oil industry records over this period.

They found that several damaging earthquakes, including a 1929 event near Whittier…