| After the 2008 earthquake, researches of mobile faults and evaluation of seismic hazardous in Sichuan Basin have caused widespread concern, especial Longquanshan fracture belt, less 20 km from Chengdu region, which through area with developed economy and dense population. Therefore it must be valuable to evaluate its seismic hazardous.Located in western Sichuan Basin, extending Leshan to Zhongjiang County, Longquanshan fracture belt is a active fault zone. It belongs to Yangtze plate as a boundary of the West Sichuan Basin and Central Sichuan uplift. Its general trend is NE20 ° ~30 ° with over 230 km length. Longquanshan fracture belt consists of western and eastern sides faults which are distributed on both sides of Longquanshan anticline. Western side faults of Longquanshan fracture belt consist of series of southeast tilted reverse faults, and Longquanshan anticline developed on upleap of it. What’s more, Longquanshan anticline is a west east steep slow fault-propagation fold. However Eastern side faults of Longquanshan fracture belt, consisting of series of northwest tilted reverse faults, form the opposite tectonization.Investigations of terrain of Longquanshan fracture belt suggests that it is west east steep slow. In addition the scale of Western side faults of Longquanshan fracture belt is more larger than eastern side faults of Longquanshan fracture belt, the fault displacement too. Thence Western side faults of Longquanshan fracture belt is dominant faults which resulted in Longquanshan anticline, and eastern side faults of Longquanshan fracture belt is only a large-scale fault zone rather than the main fault. Western side faults of Longquanshan fracture belt local has a weak activity of Late Pleistocene, where 5 earthquake occurred. Differently, evidences were not found to prove Quaternary activity of eastern side faults of Longquanshan fracture belt.Interpretation of seismic cross-sections of Longquanshan fracture belt shows that the fracture belt breaks up the surface, and its fault displacement and dip angle gradually decrease under the layer until it disappears in Leikoupo salt layers. Whta’s more, fold morphology, showed by deep seated structure, suggests that Longquanshan anticline is a decollement controlled by deep detachment; anticline and fracture belt have close genetic connection.Although academics have made lots of researches on Longquanshan fracture belt, for its formation mechanism, they have not got a unified understanding. Tectonophysi-cal Simulate is a important means to study the forming mechanism and evolution of geological structures. Through the experiment author believe that Longquanshan fault belt and Longmenshan fault zone belong to the same tectonic system. Longquanshan fault belt is the leading edge of Longmenshan fault zone, and have close connection between the compressive force passed by Longmenshan rift zone. In addition Longquanshan fault belt has been in stable period, after active period. Compared with Longmenshan tectonic belt, the degree and activity of Longquanshan fault belt are less than its. Therefore above 6 earthquake will not happen to region of interest.The spatial distribution of Longquanshan fault belt is uneven and on pregnancy of surrounding earthquake, its seismic activity has a dominant position. However lots of earthquakes in the history have happened in region of interest, destructive earthquake occurred only once, which shows that Longquanshan fault belt is a seismotectonic structure with the conditions of strong earthquake. However fault-propagation fold is on the surface which absorbs most of the slip of faults[1]. Thence there is little possibility of microseism. Combining with the consequents of Tectonophysical Simulate, the author considers that potential magnitude of the study area will not exceed 5.5. However, considering that Longquanshan fault belt is a regional fracture, one of the boundaries of structural elements, with ability of strong seismic, the author believe that maximum capacity will not exceed 6.5. |
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