Using the results of continuous long-term observations over 50 years (including solar cycles 2024), we study the relationship between Earth's seismicity and solar activity. An increase in the number of strong earthquakes on the planet occurs during the decline phase of solar activity when charged particle fluxes from high-latitude coronal holes increase, as well as during solar minimum when the intensity of galactic cosmic rays reaches a maximum. The change in the number of strong earthquakes (with magnitude 6) is considered in terms of variations in the intensity of galactic cosmic rays, Forbush decreases, and ground level enhancements in solar cosmic rays (GLE events). The number of strong earthquakes is shown to increase after Forbush decreases with a time lag from similar to 1 to similar to 6 days depending on the amplitude of Forbush decrease, and after ground level enhancements in solar cosmic rays (GLE events), the number of strong earthquakes increases by similar to 8 day. In the number of strong earthquakes, a six-month variation is observed, which seems to follow the six-month variation in cosmic rays with a delay of similar to 1-2 months. It is surmised that the relationship between solar activity and Earth's seismicity seems to be mediated through the modulation of galactic cosmic rays and atmospheric processes that provoke the occurrence of earthquakes in regions where the situation has already been prepared by tectonic activity.