Since the 1960s, the exponential increase of energy-demand has stimulated the use of new techniques for the extraction of oil and gas. However, the drawback of the massive extraction of oil is the underground reinjection of energy-coproduced wastewater. Injecting fluids underground can cause earthquakes, generally defined as induced seismicity, if those fluids find their way into fault zones that are ready to slip seismically.

The research team from the Sapienza Department of Earth Sciences, in collaboration with researchers from the University of Nice, the University of Berkeley and the California Institute of Technology, reproduced the development of fluid overpressure both on a laboratory fault and on a 300-meter-deep fault at a natural site in France.

The study, which has been published on Science Advances, analysed the fault movements in great detail during the development of overpressure and has shed light on the physical mechanisms that were largely unknown due to the impossibility of directly accessing the areas where induced seismicity occurs (ca.1 - 6 kilometres below the earth’s surface).

The researchers observed that slow aseismic deformation initiates along the pressurised fault preceding the enucleation of the induced seismic activity. In particular, aseismic deformation creates a concentration of forces on the edges of the pressurised fault that trigger micro-earthquakes.

“The development of technologies capable to monitor aseismic deformation in real time,” explains Cristiano Collettini from the Sapienza Department of Earth Sciences, “will be fundamental to allow us to implement actions to mitigate the hazard of induced seismic activity.”

References

Stabilization of fault slip by fluid injection in the laboratory and in-situ - Cappa, F., Scuderi, M. M., Collettini, C., Guglielmi, Y., & Avouac, J.P. - Science Advances 2019  DOI: 10.1126/sciadv.aau4065

Further information

Cristiano Collettini
Department of Earth Sciences, Sapienza University of Rome 
cristiano.collettini@uniroma1.it

Marco Scuderi
Department of Earth Sciences, Sapienza University of Rome 
marco.scuderi@uniroma1.it