Probing into the probability of future strong earthquake in Sichuan and Yunnan provinces from the present age character of medium-strong earthquakes stiuations

The active seismic images before the 19 strong earthquakes since 1970 occurred in onrth south seismic belts of western China and nearby regions are analyzed.Among our 19 strong earthquake cases,there are a lot of medium earthquakes happened near the epicenter areas before 9 strong earthquakes.These medium earthquakes can be divided into early period type earthquakes and impending type earthquakes.The interval between the early period earthquakes and the impending earthquake is a linear relationship with the interval between relative strong earthquakes and main strong earthquakes.Based on both formula M= 5.8+1.308×logT and special seimic indexes for medium strong earthquakes to happen in short period near the area of a strong earthquake,we try to forecast the position,magnitude and time of strong earthquake in the research area.