| The study of seismic attenuation property is a major subject in seismology. The path effect of seismic wave propagation (seismic attenuation) involves an important influential factor, the anelastic attenuation of medium, which is measured with quality factor Q, apart from geometric attenuation with the distance. As a basic physical parameter of the Earth medium, Q value is essential for quantitative study of earthquakes and source property (e.g. determination of source parameters), which is widely used in earthquake source physics and engineering seismology.There existed the osculatory relations between the seismic attenuation Q value and the crust structure features, such as the magma distribution of volcano zone, the earthquake activities, the active faults and the low velocity layer of the crust et al.. The study of the attenuation structure in the crust and the upper mantle, it will help us to understand more truly the tectonic activity, dynamic features of the crust and the upper mantle, as well as the thermal structure and the viscosity structure of the mantle. The seismic wave attenuation Q value is more sensitivity to the variation of the earth medium than the seismic wave velocity. The finely study of the three-dimensional attenuation structure, it can deepen the knowledge to the heterogeneous of the crust structure.Yunnan region is located at the southeast edge of Qinghai-Tibet plateau, the topography is high in northwest and low in southeast. It is a front zone where the India-Burma plate moves and pushes northeastward to the China Mainland, therefore, the tectonics is complicated, the strong earthquakes are very frequent in this region. The study of the activity of the historically strong earthquakes suggested that the distribution of the destructively large earthquakes in Yunnan is inhomogeneous, which are mainly concentrated at the several seismic zones or belts. The study and knowledge of the deep medium and tectonic environments for these large earthquakes occurrence, and the difference between the large earthquake-prone zones and the non-seismic zones in the deep medium and tectonic environments, it have important significance for the study of the seismogenesis, the theories and the technical methods of the earthquake prediction etc..At present, the seismic tomography method had been applied widely to the inversion of the seismic wave velocity structure. By using of this technique, it would improve greatly the study of the seismic wave attenuation Q value. Recently 10 years, a great deal of seismic waveform data had been obtained following the establishment and improvement of regional digital seismograph networks, they provide the conditions for the tomography of seismic attenuation structure.In this paper, the inversion of the seismic wave attenuation Q value in Yunnan region had been conducted by using of 1D, 2D and 3D inversion methods respectively, waveform data( June, 1999 to December, 2007) from Yunnan regional digital seismograph network.(1) The 1D inversion of Q value of S-wave anelastic attenuation in Yunnan region and its subregions had been conducted with Atkinson method and genetic algorithm, and the relations between Q( f) and frequency f in Yunnan region and its subregions had been established.(2) The 2D tomography of S-wave anelastic attenuation in Yunnan region had been conducted by using of the high-frequency attention operation t* of S wave. The algorithm and program of 2D attenuation tomography had been established. The 2D attenuation tomography of 0.5°×0.5°gridding model in Yunnan region had been accomplished.(3) The 3D tomography of S-wave anelastic attenuation in Yunnan region had been conducted by using of the high-frequency attention operation t* of S wave. The algorithm and program of 3D attenuation tomography had been established. The 3D attenuation tomography in Yunnan region had been accomplished, for the model of 1°×1°plane gridding and 0, 5,15,25,45km vertical layering.The basic characteristics and knowledge of the crust attenuation structure in Yunnan region had been achieved by this study. The results of the 1D inversion, 2D tomography and 3D tomography all indicated that there is a significant lateral heterogeneity on Q value spatial distribution in Yunnan region. Q value is relatively high in western Yunnan and low in eastern Yunnan, divided by the Jinshajiang-Honghe fault; There existed two obviously low Q zone in the northwest Yunnan (Lijiang - Yongshen - Dali - Chuxiong) and in the central Yunnan (Dongchuan - Kunming - Yixi - Huaning - Jianshui). The results of the 2D tomography and 3D tomography also indicated that there are two low Q zone in Baoshan - Tengchong and Simao - Jinhong; Lanchang - Genma zone is high Q zone. The results of the 3D tomography indicated that the depth is about 10km for the low Q zone in the northwest Yunnan, Baoshan - Tengchong and Simao - Jinhong, and about 20km for the the low Q zone in the central Yunnan. The lateral heterogeneity on Q value spatial distribution in Yunnan region, is quite consistent with the regional difference between tectonic activities, seismic activities, crustal velocity structure and thermal activities of the region. Areas with intense tectonic activities, high heat activities and low velocities are usually one of low Q values, where the seismic wave attenuation is fast.The study results in this paper also presented that there existed obviously difference on the Q structure between the strong earthquake active zone of Lanchang - Genma and that of the northwest Yunnan, the central Yunnan; the former high Q zone, and the after low Q zone. This difference same existed on the velocity structure, thermal structure and tectonic activities etc.. That suggested that there are two kinds of different medium structure conditions for the strong earthquake activity in Yunnan region.In conclusion, the methods of the 1D inversion, 2D tomography and 3D tomography for S wave attenuation had been established in this paper. The 1D inversion, 2D tomography and 3D tomography for S wave attenuation in Yunnan region had been accomplished by using of the waveform data from Yunana regional digital seismograph network, and the basic characteristics and knowledge of the crust attenuation structure in Yunnan region had been achieved. The 1D inversion result ( the relations between Q( f) and frequency f ) had been applied widely on the analysis and study of the waveform data from Yunana regional digital seismograph network, especially on the determination of the seismic source parameters. The features of the crust attenuation structure in Yunnan region revealed by the 2D tomography and 3D tomography, it provided the new data and evidence to understand deeply the medium structure conditions for the strong earthquake activity, and it suggested that there are two kinds of different medium structure conditions for the strong earthquake activity in Yunnan region.
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