Characteristics of seismic coda attenuation in Longtan reservoir of Guangxi region

This paper firstly selected 3 822 three-component records from 10 stations of Long-tan reservoir seismic network from 2006 to 2013 according to the high signal-to-noise ratio and calculation requirements. Based on the Sato single scattering model, this paper calculated the coda Q（ f ） after filtering the data and eliminating ambient noises, and then obtained the relationship between coda Q（ f ） and frequency f. Finally we anayzed the spatio-temporal characteristics of seismic coda attenuation in the Longtan reservoir area. The results show that the Longtan reservoir area is characterized by low Q₀ and high dependence index η, and its Q₀ value and dependence index η are lower than that of Shanxi Reservoir, which is consistent with the fact that the its seismic activity is higher than the latter. The spatial distribution of the coda Q value shows that Q₀ values of the stations with surrounding small earthquakes densely distributed and the stations in the areas with active historical earthquakes are lower than those of the stations with sparse distribution of surrounding small earthquakes. Further analyses on the relationship between attenuation parameters and sampling depth of the reservoir area suggest that there exist deep high attenuation layers beneath the studied area. By analyzing the change process of attenuation parameters with time, it is considered that after reservoir impoundment the coda attenuation parameters still mainly reflect the non-uniformity of the original crustal internal medium of the reservoir area, and the properties of the crustal medium have not been changed significantly, but some local sensitive points have been adjusted.