中国大陆及邻区海域地壳上地幔各向异性研究  

Anisotropy in crust and upper mantle beneath China continent and its adjacent seas

作　　者：彭艳菊[1] 黄忠贤[1] 苏伟[2] 郑月军[1] 

机构地区：[1]中国地震局地壳应力研究所,北京100085 [2]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学报》2007年第3期752-759,共8页Chinese Journal of Geophysics

基　　金：中国科学院知识创新工程项目(KZCX3-SW-234-2);地震科学联合基金课题(102019);国家自然科学基金(40274010)资助

摘　　要：利用分别由Love波和Rayleigh波得到的S波速度结构的差值(VSH-VSV)对中国大陆及邻区海域(70°E^145°E,15°N^55°N)地壳上地幔中的偏振各向异性进行研究.初步研究结果表明,各向异性在空间分布上存在不均匀性:(1)在小于150km的深度范围内,VSH>VSV的各向异性体占主导地位,反映出在地球的浅部岩石圈内的水平应力作用及软流圈顶部物质的水平向流动对各向异性的形成起主导作用.在大陆地区,各向异性的强度随深度有显著变化.上地壳和上地幔盖层中的各向异性普遍较弱,而在流变性较强的下地壳和软流圈存在较大范围的各向异性.这一现象说明下地壳在岩石圈变形中可能有解耦作用.(2)在大于200km深度的软流圈下部主要表现为VSH<VSV的各向异性,说明地幔物质垂直运动相对占优势地位.(3)在中国大陆东部可以看出一个大致趋势:在构造比较稳定的地区,岩石圈中VSH>VSV的各向异性比较显著,而软流圈中VSH<VSV的各向异性较弱;在构造活动比较强烈的地区,软流圈中VSH<VSV的各向异性占主导地位.(4)印度板块低角度向青藏高原下俯冲影响了中国大陆西部地区各向异性的特征.印度板块向北运动水平挤压中国西部大陆,使得物质定向重结晶,从而在岩石圈下部产生显著的VSH>VSV各向异性.Using the difference of S wave velocity structures derived respectively from Love and Rayleigh waves, the polarization anisotropy in crust and upper mantle beneath China continent and adjacent seas is studied. The result indicates that the distribution of anisotropy is spatially uneven. （1） The VSH 〉 Vsv anisotropy is dominant in the upper 150 km, which indicates that the horizontal stress in shallower lithosphere and the horizontal mass flow in upper asthenosphere are the leading factors in the formation of polarization anisotropy. In the land area the anisotropy intensity changes markedly with depth. The anisotropy in upper crust and upper mantle lid is generally weak, while the anisotropy is intense in the rheologically weak lower crust and asthenosphere, which indicates that the lower crust may decouple in the lithosphere deformation. （2） VSH 〈 Vsv anisotropy is the main characteristic of the lower asthenosphere beneath 200 km, which reflects the vertical movement of the mantle mass. （3） The overall picture in eastern China continent is that in stable blocks VSH 〉 Vsv anisotropy is more prominent in lithosphere and VSH 〈 VSV anisotropy is weaker in asthenosphere, in teetonieally aefive areas it is on the eontrary. （4） In western China the anisotropy is apparently related to the subduetion of India plate beneath Tibet. The eonspieuous VSH 〉 VSV anisotropy is the result of the eollision and eompression between India plate and Eurasian eontinent whieh makes the mantle material reerystalize in preferred orientation.

关 键 词：中国大陆及海域 地壳 上地幔 偏振各向异性 

分 类 号：P315[天文地球—地震学]