Characteristics and formation mechanism of the Yangjiazhuang-Maguduo ground fissure, western Linfen Basin, Northern China

The Yangjiazhuang-Maguduo ground fissure, which is in front of the Luoyun Mountain on the western margin of the Linfen Basin, is a typical ground fissure that developed in the transition zone between the basin and mountain. In this paper, the developmental characteristics and mechanisms of the ground fissure in the transition zone between the basin and mountain under the action of fault activity and pumping were studied and analyzed through ground investigation, engineering geological mapping, trenching and geophysical exploration. The investigation and research confirmed that the strike of the ground fissure is parallel to the Luoyun Mountain piedmont fault and the ground surface has both horizontal extension and vertical offset. Trench result shows that the plane of the superficial part of the ground fissure is rough, which is typical tensile failure; the plane of the ground fissure under the bottom of the trench is smooth and mainly displaying shear deformation, and meanwhile the vertical offset of the stratum increases with depth showing synsedimentary structural characteristics. Shallow geophysical results reveal that the ground fissure is a manifestation of the Luoyun Mountain piedmont fault. Research suggests that deep tectonic activity caused pre-existing faults in the Luoyun Mountain piedmont to be in a continuous tensile shear state, which enhanced their activity and caused the pre-existing faults to extend to the surface, forming the ground fissure in the hanging wall of the fault. Continuous groundwater overexploitation led to the consolidation and settlement of the hanging wall of the Luoyun Mountain piedmont fault, which increased the differential settlement on both sides of the Luoyun Mountain piedmont fault, thus intensifying the movement speed of the Yangjiazhuang-Maguduo ground fissure and forming the present ground fissure. The development characteristics and formation mechanism of the Yangjiazhuang-Maguduo ground fissure provide not only an important reference for studying ground fissures in basin-mountain transition zones, but also guidance for the prevention and mitigation of such geological disasters.