SUMMARY
The boundary between upper and lower seismogenic layers, below which large earthquakes tend to occur, is very important to estimate future seismic hazards. To estimate the depth of the seismogenic boundary, this study analyzes more than 38,000 earthquakes (M = 2.5) that occurred in mainland China from 2008 to 2016. Assuming Gutenberg-Richter distributions, a significant change of b-value was ob- tained at about the depth range of 9 km, as observed in California. East China, as a region of reliable depth, also shows the same bound- ary of 9 km with frequent occurrence of large earthquakes (M > 5).