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基于Bayes反演理论(Tarantola,1987,2005),在接收函数非线性复谱比反演方法基础上(刘启元等,1996),本文讨论了接收函数与地震环境噪声Rayleigh波相速度频散的联合反演.本文采用修正后的快速广义反射/透射系数方法(Pei et al.,2008,2009)计算Rayleigh波相速度频散,并引入地壳泊松比的全局性搜索.数值检验表明:(1)接收函数与环境噪声的联合反演能够有效地解决反演结果对初始模型依赖的问题,即使对地壳速度结构仅有非常粗略的初始估计(例如,垂向均匀模型),本文方法仍能给出模型参数的可靠估计;(2)由于环境噪声与接收函数在频带上的适配性明显优于地震面波,接收函数与环境噪声的非线性联合反演能更好地约束台站下方近地表的速度结构;对于周期范围为2～40s的环境噪声相速度频散,利用本文方法能够可靠推测台站下方0～80km深度范围的S波速度结构,其浅表速度结构的分辨率可达到1km(3)本文方法能够可靠地估计地壳泊松比,泊松比的全局性搜索有助于合理解释接收函数和环境噪声的面波频散数据.利用本文方法对川西台阵KWC05台站观测的接收函数与环境噪声的联合反演表明,该台站下方地壳厚度为44km,上地壳具有明显的高速结构,24～42km范围的中下地壳具有低速结构.该台站下方地壳的平均泊松比为0.262,壳内低速带的泊松比为0.27.
Based on the Bayes inversion theory (Tarantola, 1987, 2005) and based on the nonlinear complex spectral inversion of the receiver function (Liu et al., 1996), this paper discusses the combination of the receiver function and the phase velocity dispersion of the Rayleigh wave (Pei et al., 2008, 2009), the phase velocity dispersion of Rayleigh wave is calculated and the global search of crustal Poisson’s ratio is introduced. Numerical tests show that (1 ) The joint inversion of receiver function and environmental noise can effectively solve the problem that the inversion results depend on the initial model. Even though there is only a very rough initial estimate of the crustal velocity structure (for example, the vertical uniform model), the proposed method can still give (2) Because the adaptability of the environment noise and receiver function in the frequency band is obviously better than that of the seismic surface wave, the nonlinear joint inversion of the receiver function and the environmental noise can better restrain the position near the station Surface velocity structure. For the phase noise of ambient noise with period of 2 ~ 40s, the S-wave velocity structure in the depth of 0 ~ 80km below the station can be inferred by using this method. The superficial velocity structure The resolution of this method can reach 1km. (3) The global search of the Poisson’s ratio and the Poisson’s ratio of the crust can be reliably estimated by this method, which can help to explain the surface wave dispersion data of the receiver function and environmental noise reasonably. The joint inversion of the receiver function and ambient noise at station KWC05 shows that the crust thickness beneath the station is 44 km, the upper crust has obvious high-speed structure, and the lower crust has a low-speed structure in the range of 24-42 km. The average Poisson’s ratio is 0.262, and the Poisson’s ratio of the low velocity zone in the shell is 0.27.