An unusually shallow earthquake triggered by hydraulic fracturing in a Chinese shale gas field could change how experts view the risks of fracking for faults that lie very near the Earth’s surface.
In the journal Seismological Research Letters, Hongfeng Yang of The Chinese University of Hong Kong and colleagues suggest that the magnitude 4.9 earthquake that struck Rongxian County, Sichuan, China on 25 February 2019 took place along a fault about one kilometer (0.6 miles) deep.
The earthquake, along with two foreshocks with magnitudes larger than 4, appear to be related to activity at nearby hydraulic fracturing wells. Although earthquakes induced by human activity such as fracking are typically more shallow than natural earthquakes, it is rare for any earthquake of this size to take place at such a shallow depth.
“Earthquakes with much smaller magnitudes, for example magnitude 2, have been reported at such