SEISMOTECTONIC IMPLICATION OF SEISMICITY PATTERN

Abstract

Seismicity pattern represents the characteristics of a group of earthquakes. This paper describes several characteristic features of seismicity in China's mainland, especially in North China. They include block-like distribution of earthquakes, temporal correlation of seismic activities of given separate regions, repeat of certain seismicity pattern in space, etc. The spatial dimension of these patterns may reach hundreds or thousands of kilometers. Accordingly, the dynamic force causing earthquakes is suggested to act simultaneously on a large area. Earthquakes in China's mainland are mainly concentrated in a layer of 15-km thickness, i.e., the competent seismogenic layer. Because of the large difference between this thickness and the large horizontal dimension of seismicity pattern, the seismogenic layer can be considered as a thin shell. Since observed block-like seismicity pattern is very similar to the buckling pattern of a thin shell, we suggest that block-like pattern of seismicity is caused by the buckling of the seismogenic layer. The calculated dimension of the buckling pattern is about 500 km and it well agrees with the dimension of blocks.