Multi-dynamic mechanisms of ground fissures on marginal mountainous region in the Fenwei Basin, China

Abstract

The Fenwei Basin has developed more than 600 ground fissures of different scales, with the Ground Fissures on Marginal Mountainous Region (GFMMR) in the Basin cause the most severe damage. However, there is currently limited research on the common characteristics of GFMMR, and the formation mechanisms are not yet clear. This study utilizes geological surveys, trenching, drilling, geophysical exploration, interferometric synthetic aperture radar (InSAR), and numerical simulation, found that the GFMMR develop on the hanging wall of the marginal mountainous faults, with their strikes generally consistent with these faults, and the failure pattern of these ground fissures that near the mountain is primarily shear failure, gradually transitioning to tension failure at the distal end. Profile results show clear synsedimentary fault characteristics, and these ground fissures are connected to deep-seated faults. This study reveals that the formation mechanisms of the GFMMR in the Fenwei Basin involve two aspects: fault control and hydrodynamic triggering. The extensional stress in the NW–SE direction of the Basin, combined with the counterclockwise rotation of the Ordos block, leads to the extensional creep of the marginal mountainous faults, further controlling the exposure locations and activity intensity of the GFMMR. Human overpumping of groundwater induces uneven subsidence of the stratum, forming a series of subsidence funnels on the surface, which exacerbates the rupture and expansion of ground fissures while also accelerating their exposure through water erosion caused by rainfall. This study has essential reference value for disaster prevention and reduction of ground fissures in the Fenwei Basin.