CONTRASTIVE RESEARCH OF LARGE EARTHQUAKES ACTIVITY CHARACTERISTICS ALONG THE EASTERN EDGE AND ARCH BELT IN THE NORTH EARTHQUAKE AREA OF QINGHAITIBET PLATEAU

The seismic activity pattern showed moderately strong earthquakes occurred ups and downs for a long period,strong earthquake activity kept calm for 10 to 30 years and large earthquake would occur suddenly even without moderate earthquakes above 5.0n the contrary,in the north large earthquake area,there was moderate earthquakes increasing for ten years and large earthquakes occurred in group for 1 to 3 years before most strong earthquakes above 7.The author thought if 11 large earthquakes above 7.7(including Wenchuan 8.0 earthquake)in eastern edge of North-south earthquake belt belonged to occurring ups and downs in medium or long term and suddenly in short term,the other kind of large earthquake should be occurring by step correspondingly.The earthquake activity characteristics of Wenchuan 8.0 earthquake was reviewed and discussed on the base of the above thought.