ANALYSIS FOR MECHANISM OF GUOCHANG EARTH FISSURES IN LINFEN BASIN

Earth fissures are one of the geohazards in Linfen Basin. They firstly occurred here in 1970s.86 earth fissures were found in Linfen Basin in August, 2012. This paper examines the Guochang earth fissure. It expounds in detail the geological environment of Linfen Basin. The geological investigation, measurement, trenching, drilling and geophysical exploration are used to study the characteristics of earth fissure. They include the planes, damages, shallow sectional structure, deep features. It then summarizes the activity of earth fissure. Finally, this paper discovers the main characteristics of Guochang earth fissure. It has planar long extend, fat width, stability of trend, and severe damages. The shallow section is wide at the top and narrow at the bottom, which look likestrumpet.The deep features show the extractive activity existed in the lower part of earth fissure. The activity of ground fissure is controlled by rainfall. The effects of different factors on Guochang earth fissure are analyzed. The factors include tectonic activity, excessive extraction of groundwater and heavy rains. The formation of Guochang earth fissure is divided into the three steps of inoculation, formation and expansion. At last, the formation mechanism of Guochang earth fissure is acquired. The mechanism includes that (1)tectonic activity inoculates the fissure, (2)pumping groundwater triggers the fissure and (3)heavy rainfalls extend the fissure.