CHARACTERISTICS AND MECHANISM ANALYSIS OF EARTH FISSURES IN ANREN COUNTY IN WEIHE BASIN

During the field survey in 2016,48 earth fissures were discovered in the Anren county,North-East of the Wei River Basin. These fissures have resulted in severe geo-hazards. To determine the characteristics and the formation mechanism of these earth fissures,a series of geological investigation methods,such as field investi￣gations,measurements,seismic exploration,geological drilling,and trench excavation were employed. Field investigations and measurements indicated that these earth fissures were distributed along the geomorphic boundary and developed on the hanging wall of Shuangquan-Linyi fault. They were found to be trending in 60°~80°direction and were divided into five groups. Searches across the earth fissures revealed that multiple secondary fissures existed on both sides of these earth fissures,indicating that earth fissures caused severe soil ruptures in the shallow earth surfaces. Geological drilling profiles revealed that earth fissures dislocate several stratums and reflected that they possess the characteristics of syn-sedimentary faults. Seismic reflection profiles revealed that buried faults existed under the earth fissures,which showed that earth fissures were outcrops of buried faults. Regarding their genesis,these fissures were formed owing to the coupling action of multiple factors. The earth fissures forming process at Anren area can be divided into three stages. The regional extension first generated multiple buried faults. Then,the seismic activity ruptured multiple strata near the buried faults and formed multiple buried fractures. Finally,erosion process resulting from water infiltration caused the buried fractures to propagate to the surface and promote the formation of current earth fissures.