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This paper takes Fen-Wei Basin (FWB) as a case to study the ground fissures controlled by normal fault. Based on the field investigation, geophysical exploration, drilling, GNSS data and numerical calculation, the characteristics and mechanism of ground fissures originated from the hanging wall of normal faults are revealed. The results show that the distribution of ground fissures in the hanging wall and heading wall of the active faults is not uniform. Ground fissures are mostly distributed in the hanging wall of active faults and show a linear distribution on the surface, their strike is consistent with the fault, mainly characterized by vertical offset and horizontal tension. Ground fissures destroy the farmland and building foundation through which they pass and cause the rupture or displacement. In profile section, the ground fissure shows the characteristics of normal faults and dislocates the strata, and is connected with the underlying faults. Numerical analysis shows that the vertical displacement of normal fault activity in hanging wall is much larger than that in heading wall, which is the reason that tectonic ground fissures mainly originate from hanging wall. The range of dangerous area of ground fissures is controlled by the depth of fault, the strength of the ground fissures disaster is mainly controlled by the activity of fault. The formation of the ground fissures originated from the hanging wall of the fault experienced three stages: the main fault activity stage, the secondary fault activity stage and the fissure formation stage. [ABSTRACT FROM AUTHOR]

Dali County is located in the eastern Weihe Basin where frequent ground fissure disasters occur. Dali ground fissures are macroscopically part of the ground fissure group in the Weihe Basin and have caused serious damage to infrastructure and agricultural production in this area. In this paper, 25 ground fissures in Dali County are identified through investigation, and two typical ground fissures in Fengcun and Weizhuang are selected for research. Through field investigation, trench excavation, geophysical exploration, soil water content tests and collapsibility coefficient tests, the basic features, shallow structural characteristics, deep structural characteristics and genetic mechanisms of the two ground fissures are revealed. The strike of the Fengcun ground fissure is 45°, almost parallel to the Shuangquan-Linyi Fault; the length is 2 km, and the profile is ladder-like and extends deep with synsedimentary characteristics. The Weizhuang ground fissures are circular in plan view with a length of 315 m and trumpet-shaped in profile; they disappear in the paleosol layer. The mechanism of the Fengcun ground fissure is related to basin extension and fault activity. The ground fissures are the surface reflections of deep faults. The mechanism of the Weizhuang ground fissures is related to loess collapsibility and seepage. The Malan loess has differential settlement in collapsible and noncollapsible areas, and ground fissures are the boundary line for differential settlement of loess. Finally, based on the genetic mechanisms of ground fissures, Dali ground fissures can be divided into two types: tectonic and nontectonic. [ABSTRACT FROM AUTHOR]

[Display omitted] • An integrated method was used to examine the ground fissure. • The strike of the YJZ-MGD ground fissure was parallel to the basin edge. • The YJZ-MGD ground fissure showing a synsedimentary structure feature. • Tectonic activity and groundwater exploitation jointly drive of the ground fissure. 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. [ABSTRACT FROM AUTHOR]

A set of widely developed ground fissures within the Datong Basin, northern China, have inflicted serious damage to farm fields, roads, houses, and building foundations in Datong City. Such emergence of large-scale ground fissures is rare in urban areas. The formation mechanisms of these features were therefore investigated in detail through surveying, mapping, trenching, drilling, and geophysical prospecting. The 11 fissures in Datong City are located on the hanging wall of the Kouquan fault (part of regional horst and graben terrain), and run approximately parallel, with a dominant strike of NE34°–70° and a maximum length of 5.5 km. These structures occur in clear zones with similar directions and lateral distributions on the surface. They possess evident synsedimentary fault characteristics, including y-shaped, trapezoidal, and traction structures in their profiles. The synergistic action of different tectonic factors and groundwater exploitation is responsible for fissure formation. Under the influences of regional tensile stress, upper mantle uplift, and fault block movement, activity along local faults created hidden fracture systems within the hanging wall. The over-exploitation of groundwater in the region subsequently accelerated fracture growth, and varying vertical compressibility of the strata on both sides of the local fault resulted in uneven subsidence on the surface, generating tensile zones and promoting the appearance of fissures at the edges of settlement funnels. • Ground fissures in Datong City, China, were characterized by geophysical methods. • Fissure patterns closely followed a regional fault system. • Fault activity formed a hidden fracture system, which led to fissure formation. • Over-extraction from confined aquifers exacerbated fissure formation. • Tectonic and non-tectonic factors combined to influence fissure development. [ABSTRACT FROM AUTHOR]

The Datong Basin is part of the regionally extensive Fenwei Graben System, a major tectonic zone impacted by active tectonics and the resulting damage to life and infrastructure. The basin also contains the Shizhuang ground fissure system. In this study, the likely origin, surface extent, and fissure subsurface characteristics are explored by traditional methods: surveying, mapping, trenching, drilling, and seismic exploration. The Shizhuang ground fissure is located at the intersection of the Xiaoshikou fault and the southern Liuleng margin fault in Yingxian County. It has a length of 2.1 km, excellent continuity, and semi-elliptical surface morphology. The dislocation of strata induced by the fissure increases significantly as the depth increases. The strata bend downward and form typical traction structures near the fissure plane, indicating that the fissure has prominent synsedimentary fault characteristics. The fissure causes serious damage to houses, farmlands, roads, and public facilities, featuring large tensile cracks and vertical dislocations. The resulting data and interpretations indicate that: (1) the ground fissures connect to two major subsurface active faults, which lay the tectonic foundation for the fissure; (2) accelerated groundwater extraction has reactivated the underlying faults and exacerbated fissure development; and (3) mitigation is best achieved by cessation of excessive groundwater pumping, appropriate engineering design, and local avoidance for placement of critical structures. This paper provides a heretofore generally unknown example, promotes research on the mechanisms of fissures, and has guiding significance for disaster prevention and reduction in this area. • Various characteristics of the Shizhuang ground fissure were determined. • Trenching, drilling, and geophysical prospecting were used to examine the fissure. • Tectonic and non-tectonic factors were used to analyze the formation mechanisms. • Regional stress and fault activity controlled the development of the fissure. • Groundwater pumping and a settlement funnel accelerated the fissure extension. [ABSTRACT FROM AUTHOR]