Formation of ground fissures with synsedimentary characteristics: A case study in the Linfen Basin, northern China. (1st July 2021) - Jia, Zhijie
Graphical abstract: Highlights: Strike of ground fissure is consistent with topographic depression, indicating dependency. Tensile, offset and synsedimentary characteristics confirm correlation with existing faults. Groundwater exploitation and soil erosion aggravate the disaster triggered by ground fissure. The formation mechanism of ground fissures with synsedimentary characteristic were revealed for the first time, that is, ongoing periodic-tectonic displacement, the superposition of subsidence caused by accelerated groundwater withdrawal and soil erosion. Abstract: The Zezhang ground fissure in the Linfen Basin, China was first observed in 2004 where it damaged the infrastructure in and around the town. Field and laboratory investigations now confirm that the fissure has had a complex origin, ranging from likely recurrent fault offset with almost synchronous local sedimentation (synsedimentary), to accelerated groundwater withdrawal, soil erosion and ultimately to geomorphic expression of surface subsidence, local linear scarps and sinkholes. Trench exposures and interpretation of borehole data indicate that at least four tectonic events took place during the latest Pleistocene and Holocene generally localizing the zone of fissure expression. In contrast to other tectonic ground fissures, the ground fissures in Zezhang are highlighted with major synsedimentary characteristics. The formation mechanism of ground fissures was caused by several factors, initial and later underlying fault displacements, initial fissures with land subsidence caused by groundwater withdrawal and widening into linear sinkholes under soil erosion. The Zezhang ground fissure, its investigation techniques and the technical findings, provide a case study for assessing previously unrecognized synsedimentary fissures elsewhere.