基于细化分层法探讨面波频散曲线反演参数的简化

常规频散曲线反演过程中需要不停地改变分层数、层厚度和层速度等参数,实现过程相对繁琐,而采用细化分层法对反演参数进行简化则避免了上述缺点。具体思路为：根据目的层探测深度（如20m）将地下介质分为若干个（20个）厚度为1m的薄层和1个均匀半空间层（共21层）,这样在反演中分层数和层厚度均为已知参量,反演过程只需修改速度参数即可,避免了改变分层数和层厚度等参数,显著简化了反演计算过程。正演计算和反演结果均表明：细化分层与实际分层计算出的频散曲线是等效的,细化分层反演结果的总体效果与真实模型非常接近,这说明细化分层方法用于频散曲线反演是切实可行且有效的;将地下介质划分为1m厚的薄层,反演后每层均可得到1个横波速度,能满足反演分辨率的要求;由于实际地下介质的速度是随深度渐变的,细化分层后比按频散曲线拐点分层（每分层的厚度可能是几米或几十米,同一分层内介质的横波速度相等）更接近实际情况。

Study on Parameter Simplifying in Dispersion Curves Inversion of Surface Wave Based on Subdividing Layer Method

Such parameters as layer numbers,thickness and velocity of each layer need to be modified constantly in the conventional inversion of dispersion curves,and the realization process is relatively troublesome.Aiming at this disadvantage,a subdividing layer method to inverse the dispersion curves of surface wave is introduced.The detailed thought is as follows： according to the depth of objective layer（such as 20 m）,the underground media will be subdivided into several thin layers（20 layers） with the thickness of 1 m and a half space layer（totally 21 layers）.Then the numbers and thickness of layers are known variables in the inversion,only shear velocities need to be modified in calculation,so the inversion process is greatly simplified.The forward and inversion results indicate that the dispersion curve computed by subdividing layer method is equivalent with that by actual layer;the result inversed by subdividing layer method is similar with that by actual model.The results show that the subdividing layer method is feasible and effective in dispersion curves inversion;the underground media are subdivided into several thin layers with the thickness of 1 m,and each thin layer could get a shear velocity after inversion,so that the inversion resolution could reach;because the actual velocity of underground media changes gradually with the depth increasing,subdividing layer is more close to the actual situation than the conventional layer with the inflexion of dispersion curve（the thickness of each layer may be several meters,and the shear velocity was equal in the same layer）.