Seismic data can help us to explore earth??s inner layer structure and the physical mechanisms of earthquake, providing meaningful knowledge on evaluation and prevention of earthquakes. Furthermore, the statistical analysis of seismic data can be informed of the relevant information of crustal deformation and its depth levels. The purpose of this study was to analyze over 3 000 000 global seismic data from 1900 to 2018 recorded by the United States Geological Survey（USGS）, assuming that the seismic layers and the depth of concentrating area of earthquakes by applying frequency analysis and Gaussian multi-peaks fitting method. It was compared with nearly 2 000 000 data from 1970 to 2016 by the International Seismological Centre（ISC）and nearly 300 000 data from 2009 to 2018 by China Earthquake Data Center. The results revealed that there was a global seismic concentration area at the depth of 10 km under the ellipsoid earth surface, and the depth is consistent with brittle-ductile transition zone in the crust. The majority of earthquakes were originated within these 10 km of crust. This particular layer, in span of 10 km from earth surface, were thereby presumed as the seismic layer. In the oceanic subduction zones, another seismic concentration zone was observed at the depth of 35 km below the surface, highlighting its significant role in the lithosphere. In the shallow layers of the earth（within 40 km below the surface）, the layer structures were observed to play a significantly greater role in the earthquake generation. The 3-D seismic structure map of the oceanic crust subduction area showed the “Benioff zone” shape, indicating that the subduction mechanism might pull those rigid blocks with elastic mechanics properties to deeper layer of the earth, thereby breeding earthquakes of intermediate to deep foci. Accordingly, the distribution of earthquake foci revealed the distribution of earthquake layers which are rigid blocks in the lithosphere; in addition, the concentration area of earthquake focal depth would be the main deformation and energy release zone of the lithosphere and the middle and upper mantle.