STRESS FIELD IN THE FUYUN, XINJIANG EARTHQUAKE FRACTURE ZONE DETERMINED BY FITTING FAULT SLIP VECTOR DATA

Based on the horizontal and vertical offset data of 42 faults obtained from field survey in the epiceutral zone, caused by the great 1931 Fuyun earthquake of magnitude 8, the slip directions on the fault planes are deduced. The mean stress fields corresponding to 4 segments, from north to south, of the fracture zone have been estimated by minimizing the angle between the calculated shear stress and the observed slip vector on each fault.The result indicates that for the 4 segments the maximum and minimum compressive principal stress axes are all horizontal, while the maximum compressive principal stress axes take approximately the azimuths between N15E to N30 E. The overall stress field in the entire fracture zone is rather homogeneous, this implies that the underline cause for the great Fuyun earthquake could hardly be some local factors, but possibly tectonic movement on a large scale.