Study On The Reservoir Induced Seismicity In Chongqing Under The Running Of The Three Gorges Reservoir

Reservoir induced seismicity is induced by the reservoir,even some places experience few or no earthquakes before.This phenomenon widely occurs in many places of the world,there is obvious difference on the seismic activity level between reservoir induced seismicity and local earthquakes that before storing water, and reservoir induced seismicity has its own characteristics compared with tectonic earthquakes.At a certain period of time,especially in the initial impoundment period, there is a good relationship between seismic activities and water levels.With the completion and impoundment of the Three Gorges Reservoir,there would be enormous water body and dramatic changes in water level.This change would break the balance of the inherent tectonic stress field,lead to new faults active or revive the old ones and some geological disasters,such as seismicity and new environmental problems.So the study of reservoir induced seismicity of the Three Gorges Reservoir in Chongqing has important significance,not only social, but theoretical. In this study, choose the Three Gorges Reservoir Region of Chongqing as the research object,to study the mechanisms of reservoir induced seismicity.The results of the main contents are as follows:(1)Through summarizing the research paper,learn the history and the status quo on reservoir induced seismicity,based on the valuable theories and methods,outline the classifications and characteristics of the reservoir induced seismicity.On engineering geology,the geological structure and geomorphological information of Chongqing reservoir region and its surrounding region are collected and sorted,make sure the geological structure and the potential seismogenic fault geometry.(2)On the seismology, analyse the characteristics of the seismicity,as well as the relationships with the water level before and after the impoundment of the Three Gorges Reservoir,and study the spatial and temporal distribution characteristics and the occur- ence mechanism of reservoir induced seismicity, no matter in large scale or small.(3)Divide the load of the reservoir induced seismicity into stress load(stress of static water body,seepage pressure and tectonic stress,etc)and non-stress load(softening effect, the role of stress corrosion and lubrication,etc).According to the stress state of different parts of faults,discussed the mechanism of fault slip,in accordance with the compression region,tension region and tension-compression region,respectively.(4)Based on fracture mechanics,elasticity mechanids,etc,carry out fracture mechan- ics analysis on the reservoir induced seismicity,and set up the formulas to calculate the earquake magnitude whenever water level rises and falls separately.(5)According to the geomorphological and geological information of the Three Gorges Reservoir Region in Chongqing,used ANSYS and FLAC3D to set up three-dimensional numerical models of Chongqing reservoir region and Wushan County separately,which includes the terrain units and has also explored the changes of crustal stress field and deformation field with reservoir water load.Through the numerical simulation results of the stress field and displacement field,found that the existence of fault damage the distribution uniformity of the stress field and displacement field.The stress concentrate near the fault zone.The change of reservoir water load has significant impact on the change of the fault stress field and displacement field in the submerged region.The reservoir water load has trigger action to reservoir induced seismicity.The research has provide new methods for the search of the formation mechanism of reservoir induced seismicity in Chongqing under the running of the Three Gorges Reservoir.