STUDY OF THE SEISMICITY OF STRONG EARTHQUAKES IN YUNNAN AREA

Yunnan locates in the east margin of the collision zone between the Indian Plate and the Eurasian Plate in the Chinese continent, where the crustal movement is violent and the moderate-strong earthquakes are frequent. In addition, the area is featured with marked active block movement. Therefore, Yunnan is a perfect place for the research on strong earthquake activity. Through the study on the temporal and spatial distribution of the M6.7 earthquakes and the related earthquake dynamics in Yunnan in the last century, we conclude that the four seismically active periods which are characterized by the alternative activity in the east and the west part of Yunnan possibly result from the combination of the active and quiescent periods in each of the east part and the west part. And for every 100 years, there may be a period in which strong earthquakes occur in the east and the west parts simultaneously. Besides, the seismicity of strong earthquakes in Yunnan corresponds well to the one in the peripheral region. The seismicity of the great earthquakes in the Andaman-Burma Tectonic Arc Belt indicates, to some extent, the beginning of seismically active period in Yunnan. The seismicity of strong earthquakes in east Yunnan is closely related with the one in Sichuan. The strong earthquakes in Sichuan often occur later than the ones in Yunnan. Further, in the east part of Yunnan, the three procedures including continuous occurrence of moderate-strong earthquakes, quiescent period, and the occurrence of the first strong earthquake may be the style of the beginning of the earthquake active period. The above cognition is helpful to the study of earthquake prediction, seismogenic mechanism, and the dynamics of the plate margin in Yunnan.