The Chang Ma earthguake (M=7.5) Qccurred on December 25th, 1932 was the conseguence of the then strong movement in western Chang Ma-EBo fault zone. In this zone, the movement of the vertical displacement was more evident in its western sector than the eastern one. Since the Quaternary, the movement had shown in the way of two planes of shear fracture of the north-north west and north-west west.
The earthguake's deformation zohe expended in the direction of the planes of shear fracture. It appeared in the shape of reversed S on the plane. The north north-west deformation zone indicated a clockwise twist, while the north-west west deformation an anti-clockwise twist. This not only coinsides with the direction of the plane of shear fracture, but also conforms in the direction of twist, compared, with the two planes of shear fracture of the earthquake fault. In Gansu Corridor, when the total structure became the shape of reversed S, while the individual was not, it was one of the geological marks of the western Qi-Lü epsilon structural system that moved recently and at present.
According to the differentiation in the earthquake deformation zono at the time of the earthquake the direction of the principal compression stress was north 30°-40° east, it was similar to north 33° east, obtained by stress relief method.
Based on the geological analogical method, it is believed that since the Min Le area and Chang Ma area have similar Comditions in structure and rock, there exists the possibility of middle-strong earthquake.