Reservoir-triggered seismicity in Brazil: assessment, impacts and mitigation approaches.

• Grant number: 25/03077-1
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: October 01, 2025
• End date: September 30, 2028
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geophysics
• Principal Investigator: George Sand Leão Araújo de França
• Grantee: Haris Raza
• Host Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Achieving the goals of the Paris Agreement requires prioritizing emission reductions, with a strong emphasis on transitioning from fossil fuels to renewable energy sources. Among these, hydropower has emerged as a leading and safe renewable energy source. However, hydropower is also associated with a phenomenon known as reservoir-triggered seismicity (RTS), which poses significant challenges to safe reservoir management. The increasing number of large hydropower plants with expansive reservoirs has heightened the need for a deeper understanding of RTS, a phenomenon that continues to present management difficulties. RTS is an issue of growing concern globally, with cases being documented across numerous hydroelectric power plants and planned dams and reservoirs worldwide for over six decades. Notably, Brazil has experienced a significant number of RTS incidents, with 29 documented cases out of 185 globally, making it a focal point for RTS research. The largest recorded RTS event in Brazil occurred in November 1973, with a magnitude of 4.2, linked to the Porto Colômbia and Volta Grande reservoirs. Reservoir-triggered seismicity typically exhibits initial patterns that sometimes correlate with fluctuations in water levels, which may manifest as delayed behaviors. Although past studies have established a clear connection between triggered earthquakes in Brazil and the loading and unloading cycles of reservoirs, the underlying triggering mechanisms remain poorly understood. The existing models aimed at understanding the genesis of RTS are limited by a lack of observational data from the near-field regions of the earthquakes, highlighting the need for further exploration. Specifically, more in-depth geological studies and modeling approaches are required for RTS-prone areas, where seismic events occur within diverse lithological environments, making the understanding of seismogenesis particularly crucial. The process of pore pressure diffusion within geological formations plays a significant role in the initiation of RTS. If the pore pressure cannot effectively propagate through vertically low-permeable rocks, it can take centuries for the pressure to reach the depth at which earthquakes occur. To address this knowledge gap, the present study attempts to explore the causal mechanisms of RTS by developing a 3D reservoir model. This model evaluates the effects of reservoir impoundment on the subsurface, focusing on changes in both pore pressure and stress. Numerical simulations are employed to analyze the poromechanical response of the subsurface to the reservoir's loading, incorporating three geological rock layers extending to significant subsurface depths. By examining the potential nodal planes proposed in the model, the study aims to demonstrate how the stress regime associated with reservoir impoundment may influence seismic activity. This approach offers a new perspective on understanding RTS, with the potential to contribute to improved reservoir management and mitigation strategies for seismic risks associated with large hydropower projects.