Man-made earthquakes, so called induced seismicity, have become an increasing concern.
Man-made earthquakes, so called induced seismicity, have become an increasing concern. These events can occur during fluid injection or extraction such as in oil or gas reservoirs, wastewater disposal, or geothermal reservoirs. In few cases larger co-called ‘runaway induced earthquakes’ were strong enough to cause public concern and stopping projects (e.g. 2006 Basel/Switzerland) or even substantial damage (2017 Pohang/South Korea). Intense research, however, has resulted in successful attempts to avoid such runaway events such as in the Helsinki geothermal project in 2018. The key to systematically avoid large induced earthquakes is to better understand the underlying physical processes.
In a new study published in the Proceedings of the National Academy of Sciences, Dr. Lei Wang and his colleagues from the GFZ Section ‘Geomechanics and Scientific Drilling’, together with researchers from the University of Oslo, Norway, report that the roughness of pre-existing faults and associated stress heterogeneity in geological reservoirs play a key role for causing such runaway events. The study combines novel fluid injection experiments under acoustic monitoring performed in GFZ’s geomechanical laboratory with numerical modelling results. ‘’We found that rough and smooth faults in the rocks behaved entirely different during our laboratory experiments. This is an exciting observation as we evidenced the progressive localization of microseismic activity indicating stress transfer before large induced events during fluid injection’’, says the first author Dr. Wang who designed and performed the experiments and the modelling.
Read more at GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre
Image: Apparatus in the geomechanical high-pressure laboratory: Here, the cylindrical rock samples can be subjected to stresses that typically act several kilometres deep in the earth's crust. Even stronger stresses then trigger fault slip. (Photo credit: GFZ)
