云南高黎贡山典型板岩地震波各向异性研究  

Analysis of seismic anisotropy of slate and its application of slate

作　　者：郭彬彬[1,2] 王红才[1,2] 赵卫华[1,2] 嵇少丞[3] 孙东生[1,2] 李阿伟[1,2] 龙长兴[1,2] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]国土资源部新构造运动与地质灾害重点实验室,北京100081 [3]加拿大蒙特利尔大学工学院

出　　处：《地球物理学报》2014年第3期837-846,共10页Chinese Journal of Geophysics

基　　金：国土资源部深部探测技术与实验研究专项项目(Sinoprobe-07);公益行业科研专项经费项目(2010110701;201011070);所长基金88(DZLXJK201214)联合资助

摘　　要：板岩作为一种浅变质岩在我国有着广泛的分布，对其地震波速度的研究将有助于对这类过渡性岩石的有效区分，对于浅层地壳的各向异性研究也具有重要意义.本文对采自云南丙中洛地区的板岩样品进行了地震波速度的室内实验研究，其中部分实验是在加拿大Dalhousie High Pressure Laboratory完成.实验获得了板岩在围压10~600 MPa条件下、不同构造主方向（X，Y和Z）上的地震波速度，在围压600 MPa时，X、Y、Z三个方向的P波速度分别为6.58、6.46、5.91 km/s，平均速度为6.30 km/s，S波平均速度约为3.62 km/s，VP/VS=1.74；并初步分析了板岩地震波速度、横波分裂及其波速各向异性随着围压的变化规律，发现所测量的板岩在较低围压（〈150 MPa）时波速的各向异性随围压升高而迅速减小，主要是由于其内部微裂隙的定向排列引起的，而随着围压的继续增加（〉150 MPa时）微裂隙基本闭合，黑云母、阳起石等片状矿物的定向排列成为其地震波各向异性的主导诱因，此时（围压为600 MPa）VP、VS的各向异性分别稳定在13%、16%左右.本研究所获取的基础实验数据及所探讨的板岩地震波性质将为确定地壳上部显微裂隙的优选定向、浅层地壳的各向异性分析、地球物理模型条件约束等提供基础.As a special type of low-grade metamorphic rocks, slate has a wide distribution in China, which is limited between the layered shale and schist. The therefore the fine distinction of such transitional rocks by the anslysis of its seismic properties is thus very important and it will help for the study of the upper crust anisotropy. Measurements of P- and S-wave velocities （VP and VS） and their directional dependence （shear wave splitting and velocity anisotropy） of the slate samples from Bingzhongluo, Yunnan,were performed during both pressurization and depressurization in laboratory at hydrostatic confining pressures up 10 to 600 MPa using the pulse transmission technique.Wave velocities in different directions were obtained （X is parallel to the stretching lineation, Y parallel to the foliation but perpendicular to the lineation, and Z normal to the foliation）,and the VP of the slate in X,Y and Z are 6.58,6.46 and 5.91 km/s, respectively; with an arerage VP value of 6.30 km/s. The mean VS is 3.62 km/s, yielding VP/VS=1.74. The pressure dependence of P- and S-wave velocities, seismic anisotropy and shear wave splitting in the slate rocks were observed and analyzed in this paper, and their relationships have been described. For the samples, both the pressurization and depressurization （anisotropy-confinig） curves display a rapid, nonliner increase in velocity with pressure at low pressure which was caused by the closure of microcracks in samples with increasing hydrostatic pressure, and then increase slowly and linearly in velocity at high pressures which the lattice preferred orientation of the constituent minerals such as mica and actinolite became the main factor. The anisotropy of the VP and VS reached 13% and 16%, respectively. The seismic properties of the slate documented in this paper will help the development of geodynamics, earthquake monitoring, and resource exploration, and also provide an experimental basis for the fine distinction of lithology in the upper crust.

关 键 词：板岩 地震波速 各向异性 横波分裂 微裂隙 

分 类 号：P315[天文地球—地震学]