Combined approach of poroelastic and earthquake nucleation applied to the reservoir-induced seismic activity in the Val d’Agri area, Italy

In this work, an approach is developed to study the seismicity associated with the impoundment and changes of a water reservoir (reservoir induced seismicity, RIS). The proposed methodology
features a combination of a semi-analytical poroelastic model with an earthquake nucleation approach
based on rate-and-state frictional law. The combined approach was applied to the case of the Pertusillo
Lake, located in the Val d’Agri area (Italy), whose large seasonal water level changes are believed to
induce protracted micro-seismicity (local magnitude ML < 3). Results show that the lake impoundment
in 1962 could have produced up to 0.5 bar changes in Coulomb failure stress (DCFS),
while the seasonal water level variation is responsible for variation up to 0.05 bar. Modeling results of the
seismicity rates in 2001- 2014 show that the observed earthquakes are well correlated with the modeled
DCFS. Finally, the reason that the seismicity is only observed at southwest of the Pertusillo Lake is
provided, which is likely attributed to different rock lithologies and depletion caused by significant
hydrocarbon exploitation in the northeastern sector of the lake.