简正模频率的地壳改正效应

该文通过对CRUST2.0+PREM 16200个区域一维地球模型简正模频率的计算,得到简正模非线性地壳改正效应.结果表明:地壳改正的非线性化改正不可或缺,对于低频简正模,其影响较小;对于高频简正模,其影响较大,这一变化遵循能量密度函数分布规律.此外,该文将CRUST2.0网格数据展开成球谐函数,并在此基础上计算了地壳侧向非均匀导致的二阶谱峰分裂系数.将其与地幔对应系数比较得出:前者造成的简正模谱峰分裂通常远远小于后者;地壳造成的二阶谱峰分裂主要贡献来自于间断面地形起伏(地壳厚度等)而非地壳的侧向非均匀参数扰动;在反演地幔结构时必须扣除地壳对简正模谱峰分裂系数的影响.

The effects of crustal corrections on normal modes' frequencies

In this paper, the global 3D crust model CRUST2.0 was imposed on PREM so that 16200 local 1D Earth models were generated. The nonlinear crustal corrections were built through computing their corresponding frequencies. The results implied that the crustal correction were necessary. The center frequency misfit due to nonlinear crustal correction is relatively small for the low frequency normal modes while it becomes large with the overtone and angular degree improving which obeys the energy distribution discipline. Then the second order splitting coefficients of mantle had been computed and compared with mantle. The results demonstrate that the crustal splitting coefficients are often far less than mantle's. The dominant contribution is from the discontinuity of crust rather than the lateral heterogeneity. It's necessary to proceed the crustal corrections when inversing the structure of mantle.