The formation and evolutionary process of earth fissure group in Dacheng County, Northern Hebei Plain, China

Abstract

Nearly a thousand earth fissures have developed in the Hebei Plain, with a total length exceeding 100 km, making it one of the most severely affected areas by earth fissure disasters in China. Approximately 70 % of the earth fissures in the Hebei Plain are tectonic in nature, among which the earth fissure groups in Dacheng County are a typical example, causing significant economic losses locally. To reveal the genetic mechanisms of the earth fissure groups in Dacheng County, methods including historical data collection, geological surveys, measurements, trenching, drilling, geophysical exploration, and InSAR were employed to investigate their development process and analyze the evolution of controlling factors across different periods. The results show that the current earth fissure group in Dacheng County consist of eight earth fissures, predominantly striking NE and parallel to Dacheng faults, with a total length of 5 km. Most earth fissures are located on the hanging wall of faults, with damage manifested as field ruptures and sinkholes, primarily causing tensile damage to buildings. On shallow profiles, there is no significant vertical displacement of strata, but faults are present at greater depths and correspond to the locations of the main earth fissures. The development of the earth fissure groups in Dacheng County is considered to have occurred in three distinct stages. Initially, the first exposure of the earth fissure groups was triggered by seismic forces that activated the underlying faults, resulting in numerous vertical fractures within the overlying soil. Some of these vertical fractures extended to the surface, forming earth fissures, while others remained concealed, laying the structural foundation for the continued development of the earth fissure groups. Secondly, the overpumping of groundwater led to differential settlement of the soil layers, accelerating the exposure and expansion of the earth fissures. Finally, significant surface water from heavy rainfall and irrigation infiltrated through the fractures, with intense water erosion causing the earth fissures to repeatedly expose at the surface. This study has significant guiding importance and practical value for the research and prevention of earth fissures in the Hebei Plain.