Earthquakes triggered by human activity have been happening in Texas since at least 1925, and they have been widespread throughout the state ever since, according to a new historical review of the evidence. The earthquakes are caused by oil and gas operations, but the specific production techniques behind these quakes have differed over the decades, according to Cliff Frohlich, the study's lead author and senior research scientist and associate director at the Institute for Geophysics at the University of Texas at Austin. Frohlich said the evidence presented in the SRL paper should lay to rest the idea that there is no substantial proof for human-caused earthquakes in Texas, as some state officials have claimed as recently as 2015.