Abstract:North China is delineated here by a geological block roughly from 30° to 42° north latitudes and from 105° east longitudes toward east up to sea area. The data of focal mechanisms, geodetic results, ground fractures during earthquakes, isoseismals and new tectogenesis were gathered and analysed. The conclusion that the basic stress field in the crust of North China is quite consistent with compressional axis in the northeast-east direction and tensil in the north-northwest direction and these axes are nearly horizontal was drawn. The relation between the stress field and the medium defines the crustal movement. One of results of the movement is the occurrence of earthquake. From this point of view, the general features of seismisity of North China was discussed. The high and low-tides, the alternately, concentrative activities in various areas, the regular orientations of fault planes and the regular migrations of epicenters appeared in the seismic activity. They are useful for the long-term earthquake prediction.
The general features of seismogenic process for a great earthquake has been discussed combining with the various phenomena appeared before the Tangshan Earthquake. There were no foreshocks for the most of M ≥ 6 earthquakes of North China. It seems that the long period movement or creep is probably a more universal basis of precursors. On the basis of this some suggestions concerning the future work have been proposed.
