Jiangxi Upper Crust Three-dimensional Velocity Structure Seismic Tomography

Jiangxi Province is located in the middle and lower reaches of the Yangtze River,across the Yangtze Block and the South China orogenic belt, the territory Pingxiang-guangfeng fault will be divided into two parts, the northern part belong to the Yangtzeblock, the southern part belong to the South China orogenic belt. The northern region islocated in the Lower Yangtze plate and the transfer of South China orogenic belt suturezone, depression zones and fault zones development; South China Orogen experienced alot in the long geological evolution of plate stitching, tensile fracture and accompaniedby occasions The strong tectonic-magmatic events evolution, the formation of complexgeological structure of the South China orogenic belt. Several strong regional geologicalactivity had happened in the region of Jiangxi complex geological structure, making itbecame one great base of metal and the rare metal mineral. With economic development,the demand for mineral resources continues to increase, the largest province of Jiangxi asmineral resources, strengthening the mineral exploration and to improve the stock of theprotection of the country’s economic development is of great significance. Updatetechnology and equipment, mineral exploration is the transition to deep prospecting stage,deep prospecting understanding of the deep geological structure and regional tectonic putforward higher requirements. Seismic tomography is an important means ofunderstanding of the deep and the regional tectonic and seismic tomography work, so inJiangxi important to the understanding of the deep and the regional geological structure.Jiangxi region is also earthquake-prone areas, especially in the northern the Jiujiangregion and southern Gannan region earthquake deep geological structure is closelyrelated to the significance of the seismic tomography revealed the deep structure of theearthquake disaster prevention and mitigation.This article describes the basic features of the Jiangxi regional tectonic andgeophysical characteristics, the development of seismic tomography, principles, theinitial model, the forward ray tracing method, Jiangxi velocity structure of the initialmodel, compared simultaneous algebraic reconstruction method characteristics andapplicable conditions and damped least squares method Two inversion methods obtained simultaneous algebraic reconstruction method converges slowly damped least squaresmethod calculation speed, multi-faceted evaluation results, the through geological modelapplies, choose the small LSQR as this inversion method. In Jiangxi province over thepast decade seismic phases body wave longitudinal wave (wave) data, combined withexisting geological data in Jiangxi province to establish the initial model for inversionstudy, obtained from different depths of Jiangxi structure diagram and the latitude andlongitude direction of the velocity structure of the profile. Through research, thefollowing two conclusions:1. The use of the method of least squares can get Jiangxi seismic tomography results:within the range of the layers of the Jiangxi Province and its adjacent areas, the velocityin the range of three large low speed, High-speed zone are three.2. Simultaneous algebraic reconstruction method has stable convergence results, butthe memory demand, slow convergence; damped least squares method has the advantagethe balance parameter convergence speed can be adjusted, a small amount of calculation.According to the actual situation, choose damped least squares method as the inversionmethod.