THE ESTIMATION OF STRESS DROPS OF SMALL EARTHQUAKES BEFORE AND AFTER XINGTAI 5.8 EARTHQUAKE OF NOV.9,1981

Xingtai 5.8 earthquake of Nov.9, 1981 occured in the active area of Xingtai 1966 swarm of strong carthquakes, and more than 15 years after 1966 mainshockes.In this paper,the stress drops of small earthquakes before and after this earthquake (from Oct.1, 1980 to Dec.31, 1981) were estimated by the method of time range.The re-sults show that the stress drops of these earthquakes have no considerable change.In the paper, tbe above results about source parameters were discussed briefly.