剪切波在双层方位各向异性介质传播中分裂参数的变化特性

以质元运动方程和应力应变关系为基础建立了各向异性介质的波动方程．从数学上对体波在各向异性介质中的传播进行了严格的数学推导，给出了各向异性介质中三种体波波速与介质弹性常数及波传播方向的数学关系．由此对剪切波在单层和双层弱方位各向异性介质中的分裂行为进行了系统讨论，给出了合成分裂参数、每一层分裂参数与入射剪切波偏振方向的数学表达式．假定每一层分裂参数之后，得到了合成分裂参数随入射方位角变化的合成地震图．研究表明，剪切波在双层各向异性介质中传播时产生的两对分裂剪切波可用一合成分裂因子来描述．由合成分裂因子确定的分裂参数随入射剪切波偏振方向的变化呈现出π／2的变化周期．其结果可用于双层各向异性介质反演研究，对进一步解释板块运移、地幔对流规模、深源地震成因、浅部地震构造及深部力源问题等有参考意义．

THE CHARACTERISTICS OF SHEAR-WAVE SPLITTING PARAMETERS IN THE PRESENCES OF TWO WEAK AZIMUTH ANISOTROPIC LAYERS

Based on the balance equation and stress-strain relationship, this paper sets up the propagation equations of body waves in amsotropic mediuxn, and gets the exact solusions of the velocities of the three body waves varying with the medium's elastic parmeters and direction of wave propagation. Based on this, Studies the chameteristics of shear wave splitting parameters in the presences of one and two weak azimuth anisotropic layers, and gets the analytical solutions of synthetic splitting parameters varying the individual splitting parameters of the two layers and the incident azimuth angles. Assumed splitting paraxneters of each single layef, getS thesynthehc diagrarns. StUdied resultS reveals four individua waves split in the case of two weak azimuth anisotropic mediums can be described by a splitting operator. The synthetic splitting parameters exhibt systematic variations as a function of incoming polarizahon with π/ 2 periodicity, as differs from single anisotropic medium. The derived expressions can be used to invert for the individual properties of the two layers in many circurnstances and explain plate movement mantle convection scale, deep earthquake cause, shallow earthquake tectonics and deep foree source.