Dynamical changes of earthquake types during strong shockpre paration processes and relavant experimental research

The dynamic changes of earthquake types during strong earthquake preparation processes since 1965 in Yunnan were discussed.It was found that more than two M5.0 double earthquakes or swarm earthquakes occurred several months or years before M≥6.0 strong earthquakes.Part of strong earthquakes at least three preceding main shocks densely happened several months or years ago.All strong earthquakes occurred 150?km outside the areas where the preceding main shocks,double or swarm earthquakes located.The trace studies of earthquake kinds ever the typical areas indicated that M6.5 and M≥7 earthquakes always happened after M5.0 double and preceding main earthquakes occurred in Ninglang area and M6.0 swarm earthquakes occurred in Tengchong area.How ever the earthquakes located at areas which were more than 200?km far from the Ninglang and Tengchong areas.In rock rupture-type experiment,the rock samples experienced poly-rupture process orderly including the main and after crack,lone crack,swarm crack and preceding crack with load increasing.The experimental results and earthquake examples suggested that the seismic styles were relantive to both the geological structure in the seismic region and the stress conditions of in crust materials.