Earthquakes occur cyclically. In a certain region, earthquakes may occur more frequently and with greater intensity during a certain period, while they may occur less frequently and with weaker intensity during another period, that is, active periods and quiet periods alternate. Taking China in the 20th century as an example, the years 1966–1976 were a decade of frequent earthquake activity, with destructive earthquakes occurring successively in Xingtai, Tonghai, Lushuo, Yongshan, Haicheng, Longling, Tangshan, and Songpan. After that, earthquake activity in mainland China entered a relatively quiet period.
Why do earthquakes occur cyclically? Because earthquakes are a process of rapid release of underground energy. The underground rocks in a region will deform after being subjected to forces, but this deformation is slow and gradually accumulated. Only when the deformation exceeds the strength of the rocks will the rocks rupture, and the entire rupture process is often concentrated in a short period of time, triggering major earthquakes and a series of aftershocks. After the energy is released through earthquakes, the underground rocks will readjust and begin to accumulate energy again, waiting for the next eruption of earthquakes. This is how earthquakes occur cyclically.
Earthquakes always occur in a regular yet random manner. It's worth noting that the internet has made news spread faster and faster, allowing more people to learn about earthquakes in a timely manner, which gives us the illusion that earthquakes are more frequent than before. In addition, in recent years, some major earthquakes have occurred in densely populated areas, which has also made people pay more attention to earthquakes than before.