Texas Earthquakes by Scott D. Davis, Cliff Frohlich 2003 [A piece that mentions the 1932 Wortham earthquake.] [Page 31] "In contrast, petroleum production probably did induce at least two earthquake sequences in this region. On 9 April 1932, a magnitude 4.0 earthquake occurred near the towns of Wortham and Mexia, 60 km east of Waco, with a location directly within the large Mexia oil field. This field, discovered in 1920, taps one of at least ten structures in Limestone, Freestone, and Navarro counties that were formed by the northeast-trending Mexia fault system. At the time of the earthquake the Mexia and nearby Wortham oil fields had produced 90 million barrels and 22 million barrels of oil, respectively (National Oil Scouts Association 1932). ..."