Abstract: In this paper, isoseismic lines, aftershock areas of strong earthquakes in Sichuan-Yunnan area and North China with their Seismotectonic environment have been compared and studied. The main results are: ① Both the rates between the length and the width of isoseismic lines, and the lengths of aftershock area of strong earthquakes are related to the lengths of their seismogenic faults, and are related to their magnitudes too. ② The rates between the length and the width of isoseismic lines of strong earthquakes are also influenced by overburden in the region, but the lengths of aftershock area of strong earthquakes are not influenced by overburden in the region, maybe the latter can mainly reflect distribution of the seismogenic fault and nearby deep small faults.

Key words: Isoseismic line, Aftershock area, Seismotectonic environment, Seismogenic fault