A DISCUSSION ON THE FRACTURE DIRECTION OF THE DATONG-YANGGAO M6.1 EARTHQUAKE GROUP OCCURRED IN 1989

In this paper, a discussion is made on the fracture directions of the M5.7, M6.1 and M5.1 earth-quakes in the Dation-Ranggao seismic sequence according to the epicentral distribution of the after-shocks, focal mechanism solutions, wave forms, isoseismic distribution, ground fissures and geological data.It has been considered that the fracture direction of the M5.7 earthquake is nearly EW, and that of the M6.1 and M5.6 earthquakes is NNE, these two groups of fractures formed a conjugate shear frac-ture, the Datong-Yanggao seismic sequence occurred right on the plane of the conjugate shear fracture.In October 18-19 in 1989, in Datong-yanggao region in Shanxi Province successively occurred the M5.7, M6.1 and M5.6 earthquakes.After the earthquakes, the Author participated in the work of the earth-quake analysis and prediction group in situ.In the work, the author found that the fracture directions of the M5.7 M6.1 and M5.6 earthquakes are not consistent, so it is neccesary to make a discussion on it.