Earthquakes are the sudden release of enormous energy in nature. Taking the Tangshan earthquake in 1976 as an example, an earthquake with a magnitude of 7.8 on the Richter scale is equivalent to the energy released by thousands of atomic bombs. Therefore, from an energy perspective, it is very difficult for human activities to induce earthquakes, especially major earthquakes. Most earthquakes occur thousands, tens of thousands, or even hundreds of thousands of kilometers underground, while humans mainly live on the Earth's surface. It is very difficult to change the stress state of underground rocks through surface activities, which is somewhat like "a gnat trying to shake a huge tree".
However, the possibility of human activities inducing earthquakes does exist. This is because there is always a moment of rupture in the fault where earthquakes occur. If the changes in the crustal stress field caused by human activities happen to be the "last straw that breaks the camel's back", it is possible to trigger earthquakes. A typical example is earthquake-induced reservoirs. Earthquake-induced reservoirs refer to the significant increase in seismic activity in the reservoir area or adjacent areas caused by water storage in reservoirs. The earliest research on earthquake-induced reservoirs was conducted in 1931, when the Marathon Reservoir in Greece induced earthquakes. China's research on reservoir earthquakes began with the Xinfengjiang Reservoir. In 1958, China built a large reservoir in Xinfengjiang, Guangdong. After the dam was completed, many small earthquakes occurred in the reservoir and dam area. The earthquakes intensified as the water level rose, and a magnitude 6.1 earthquake occurred in 1962. Fortunately, preventive measures had been taken to reinforce the dam beforehand, and the reservoir withstood the earthquake. However, only a few reservoirs can induce earthquakes. There are more than 10,000 reservoirs built worldwide, and only 101 of them have induced earthquakes, with the maximum magnitude being 6.4.
The intuitive reason for earthquake-induced reservoirs is that water storage changes the load on the rocks at the bottom of the reservoir. The higher the water level, the greater the pressure on the rocks at the bottom of the reservoir. Moreover, reservoirs raise the groundwater level in the surrounding areas, reducing the friction between faults, making it easier to produce slippage than before water storage. In short, water changes the original stress state and physical properties of the faults, thereby altering seismic activity. Reservoirs with small storage capacity are less likely to induce earthquakes, and even if earthquakes occur, the magnitude is usually small, often below the seismic resistance of the dam, so the possibility of dam failure is also very small.