How can a large reservoir trigger an earthquake?

The filling of large reservoirs, particularly those exceeding 100 meters in depth and 1 cubic kilometer in volume, can trigger local seismicity in areas where regional tectonic forces have already strained rocks to the point of near-failure.1

This phenomenon, known as reservoir-induced seismicity, is generally attributed to two primary factors:

• Pressure Perturbation: The weight of the water in the reservoir adds stress to the underlying crust.12
• Pore Pressure: More significantly, water can seep into the ground, increasing groundwater pore pressure. This reduces the frictional strength of the rock along existing faults, allowing them to slip more easily.12

While these induced tremors are typically minor, they have been documented at several major sites, including the Hoover Dam, the Aswan High Dam, and the Kariba Dam. Although the filling of most large reservoirs does not produce hazardous earthquakes, engineers must account for these potential seismic risks during the design and monitoring of modern dams.12