The Trend Prediction for the First Active Period of Large Earthquakes in Yunnan During 21 Century

On the basis of the relation between the solar activity and the seismic activity, it is well known that under the modulation of the periodic solar activity, the earthquakes also show the periodic activity.Besides the 11-year cycle, the seismic activity has another cycle of 22 years which formed four seismic active periods and four quiet periods in 20 century in Yunnan.The active period of large earthquakes has occurred during the even number cycle of the solar active cycle, especially, during the descent phase of such cycles.Thetime interval between the last active period of the large earthquakes and the next one was about 15.9 years.During a seismic active period in Yunnan, the time interval between two large events gradually became shorter. According to the rule of earthquakes happened before, the trend prediction for the first active period of large earthquakes in 21 century in Yunnan is made in this peper as follows (1)Because the next solar activity period, i.e.24th cycle will come at about 2006, and reach the peak at about 2010, the first active period of large earthquakes in Yunnan during 21 ceutury will occur in 2012.This is the year for the descent phase of the even number cycle of the solar activity and also the year from the last large earthquake (in Lijiang in 1996)for 16 year interval.(2)During this large seismic active period, there will be several large earthquakes (M≥7.0) and a number of small earthquakes.The time interval of large earthquakes will follow the law of T_x=(T_n-T_n-1)^1/2(year).