On 3 September 2016, a magnitude 5.8 earthquake struck just northwest of Pawnee, Oklahoma, causing moderate to severe damages in buildings near the epicentre. It was the largest ever recorded in the state.

The Pawnee earthquake followed the dramatic increase of seismic events in the central United States beginning in 2009, associated with the increase of underground wastewater disposal by oil and gas operators. This and other events in the area raised public concerns and led governmental agencies to shut down injection wells and establish new regulations regarding wastewater injections.

While human-caused earthquakes have been documented for more than a century, their increasing number reported worldwide has drawn much scientific, social and political attention. Such earthquakes are related to industrial activities such as mining, construction of water dams, injection of liquids such as waste water and carbon dioxide, and extractions associated with oil and gas exploitation.

With the ever-increasing demand for energy and mineral supplies worldwide, the number of human-caused earthquakes is expected to rise in the upcoming years. Some of the largest and more destructive earthquakes of the past few years have been related to man-made activities, such as the 2008 magnitude 7.9 Wenchuan (China) earthquake and the 2015 magnitude 7.8 Nepal earthquake.

In most of the cases industrial activities do not induce earthquakes. But this becomes problematic when such activities are close to active faults. In this case, even small stresses underground caused by man-made activities can destabilise faults, inducing earthquakes.

Why does the passage observe that more human-caused earthquakes are expected?