The Study On The Earth Fissure Risk Zoning In Taiyuan Basin

Taiyuan Basin is a Cenozoic fault basin located in the center of Fen-Wei Basin, it is also a famous birthplace of earth fissures in our country. It has developed 107 earth fissures and caused as much as 300 million yuan economic losses, and its unique geological structure background has attracted many experts and scholars at home and abroad. As research continues, we have made some progress about earth fissures on the distribution characteristics, development regularities, activity characteristics and formation mechanism. However, the causes of earth fissures are complex, and the extent of the impact of the factors on earth fissures is different, so quantitative evaluation to predict the risk of their activities is badly in need, which can also provide theoretical support for disaster prevention and mitigation, and risk control work.This paper is based on the investigation results of the Project "Comprehensive research of formation mechanism and disaster reduction on earth fissures in Fen-Wei Basin", I drew a series of 1:200000 fracture, strata, landform, land subsidence and distribution maps of earth fissures, and clarify the quantitative relationship between different hazard-formative factors in Taiyuan Basin. Then I made out the risk zoning using the GIS spatial analysis technology and the fuzzy mathematics method, the main research results are as follows:(1) The Qingxu-Jiaocheng part of Jiaocheng Fault actives fastest in Taiyuan Basin, with an average rate of more than 1.3 mm/a; The geomorphic unit that has most earth fissures is piedmont alluvial-diluvial plain, which accounts for 63.55% of the total; There are four main subsidence areas, located at the south of Taiyuan City, Qingxu-Jiaocheng Area, Qixian-Taigu Area, Jiexiu-Xiaoyi Area, and the maximum subsidence rate reaches 30 cm/a.(2) Taiyuan Basin contains nine high-risk areas of earth fissures, they are located at Yijing-Jinci Area at the northern end of Jiaocheng Fault and the west of Taiyuan City, Xiaodian Area located in the south of Taiyuan City and near Tianzhuang Fault, Qingxu-Jiaocheng Area along the Jiaocheng Fault zone, Wenshui Area, Fenyang City-Xinghua Village Area, Jiexiu-Xiaoyi Area along Sanquan Fault zone and the southern subsidence region, and Yuci Area in Jinzhong City. The total acreage of risk zones is 1339.55 km2.(3) Transition zone between basins and mountains, hanging wall of fault at basin edge, zone of landscape boundary, and the edge of the subsidence funnels are high-risk areas in Taiyuan Basin for development of earth fissures, these regions are easy to induce new fissures.(4) The west of Jiexiu, the east of Xiaoyi and the southern suburb of Taiyuan City are key areas for earth fissures in the further; the activity of Tianzhuang Fault may be ignored by the outside world, and the high-speed of land subsidence in Xiaodian Area may be the "after effect" of the activity of Tianzhuang Fault in the late middle pleistocene.(5) To some extent, strata limits the extent of the development of earth fissures on surface as a medium, but is not decisive.