【摘要】 地震波各向异性日益成为不可忽视的地质地球物理现象。地球内部不同圈层(地壳、地幔和地核)都存在着地震波各向异性,并表现为不同的规模(小到单矿物和岩石,大到地体甚至上地幔)和强度。通过地震波各向异性可以间接获取岩石圈厚度、地球深部结构与构造变形、地球动力学和地幔对流等信息。主要从地震波各向异性的表现形式、原因及地质地球物理意义等方面对近年来大洋俯冲带、大陆裂谷、地幔转换带和大陆碰撞造山带(青藏高原)等构造环境中的研究成果进行了评述,讨论了各向异性研究中需要重视的几个问题:①剪切波分辨率;②矿物组构研究;③其它各向异性成因机制。还强调了各向异性研究与流变学、高温高压岩石物理实验相结合的新方向。更多还原

【Abstract】 Seismic anisotropy has received a lot of attention from seismologists in recent years and is becoming increasingly important in the field of geophysics and geology. It is regarded as the bridge between seismology and structural geology. Seismic anisotropy is discovered at all scales in the Earth’s interior and may provide us with valuable information, such as the thickness and structure of lithosphere, mantle convection, and geodynamics, and since the fast wave propagation directions of shear wave correspond to flow directions as implied from plate motions, it is recognized as a good indicator of deformation and mantle flow. Seismic anisotropy plays a central role in revealing the deep structure and geodynamics in the following geological settings, such as subduction zone, continental rift, mantle transition zone and continental collisional orogenic belt (for instance, Tibet). This paper mainly reviews recent studies of the occurrence, geological interpretation and implication of seismic anisotropy for these geological settings. There is no doubt that the existing technologies will be refined and developed further to make estimates of anisotropy and related rock properties more accurate. Problems required to be further considered include the following: (1) resolution of shear wave: SKS wave is poor in vertical resolution, and it is suggested that the combination of surface wave and SKS wave may well constrain the depth of anisotropy; (2) petrofabric analysis: although great advances had been made in investigation of relationship between anisotropy and petrofabric, recent studies reveal that olivine fabric may be different from previously expected under water-rich conditions, which may then induce anomalous seismic anisotropy. Thus, efforts are still required to be taken to further study the petrofabric, and (3) other mechanisms for seismic anisotropy, such as MPO, aligned cracks, etc.. In particular, strain aligns highly anisotropic minerals, such as olivine, orthopyroxene, plagioclase, and so on, in the mantle and crust to form LPO, which is the most likely cause of splitting measured from records of distant earthquakes. As a result, it is emphasized that investigation of seismic anisotropy shall be combined with rheology of rocks and minerals at high temperature and pressure.更多还原