The Earth is divided into three layers: the central layer is the core, the middle is the mantle, and the outer layer is the crust.

The average radius of the Earth is about 6370 km, and the thickness of the crust is about 35 km. Most destructive earthquakes occur within the crust. However, earthquakes do not only occur in the crust, but also in the soft current layer. According to seismic authorities, deep source earthquakes generally occur 300-700 km underground. To date, the deepest known source is 720 km. From this point of view, the traditional theory of plate compressional stratigraphic rupture does not reasonably explain deep source earthquakes, because there is no solid material at a depth of 720 km. Scientists envision mapping the Earth's rocks, which would be of great help in predicting earthquakes.

Previous：Earthquake precursors

Next：Major Seismic Zones in China