Mechanism of Fuping ground fissure in the Weihe Basin of northwest China: fault and rainfall

The special geological conditions of the Weihe Basin, located in the southern Fenwei Graben System, are the cause of many of the ground fissures developing in this area. The Tingzi ground fissure in Fuping County is one of the typical and particular ground fissures found in the Weihe Basin. The ground fissure is famous for its sudden appearance after heavy rainfall. To explore the characteristics and mechanism of the fissure, some geological methods were carried out in the study area for this study, such as surveying, mapping, trenching, drilling, and seismic exploration. The main conclusions are as follows: (1) the fissure is located on the hanging side of the secondary fault of the Liquan–Pucheng–Heyang fault, with a NE40°–NE75° strike and a length of 2.7 km. (2) The fissure is steeply inclined and presents a “funnel” shape in the shallow strata. There are many secondary cracks near the main fissure. (3) The fissure is connected with underlying fault and possesses the characteristics of synsedimentary faults reflecting the historical stages of fissure activities. (4) The fissure destroys farmlands and houses along the fissure, and mainly causes tensile damage. (5) The fissure was controlled by regional extension and fault, and it was promoted and enlarged by rainfall and other influential factors.