摘要
利用中国地震科学台阵第一期(2011-01-2014-06)及部分中国地震科学台阵第二期(2013-02-2015-12)的流动地震台阵记录到的小震波形资料,运用剪切波分裂系统分析(SAM)方法,分析南北地震带的地壳各向异性,对剪切波分裂参数所反映的区域应力环境及构造特征,以及区域内主压应力方向与断裂分布的关系展开讨论.研究结果表明,南北地震带快剪切波偏振方向自北向南由NE向逐渐转变为NNW向,与南北地震带区域主压应力的方向变化具有一致性.区域内分布的大量NE及WNW或NW向断裂构造同样对快波偏振方向有比较大的影响,位于走滑断裂附近的台站,其快波方向与断裂走向大致平行,部分位于走滑断裂附近的台站其快波方向几乎垂直于断裂走向,而与构造应力场方向一致性较好.个别台站表现出复杂快波优势方向特征,反映出研究区内构造环境的复杂性.慢波时间延迟结果显示,南北地震带南段的平均时间延迟高于北段,反映了受印度板块和欧亚板块的碰撞挤压作用,南段地壳介质各向异性程度更大,构造变形更加剧烈.对比南北地震带上地幔各向异性特征,推测在川滇菱形块体内部可能存在复杂的壳幔耦合现象,地壳剪切波分裂除了反映区域应力特征,还可以揭示出区域构造信息.
In this paper, the data from temporary seismic stations in the North-South seismic zone set up under the project ChinaArray PhaseⅠ（2011-01—2014-06） and the project ChinaArray PhaseⅡ（2013-02—2015-12） are analyzed with the Systematic Analysis Method of shear-wave splitting （ SAM method ） to study the crustal anisotropy of the North-South seismic zone. The environment of regional stress and the tectonic characteristics revealed by shear-wave splitting parameters are discussed as well as the relationships between regional principal compressive stress directions and fracture distributions. The results show that the fast shear-wave polarization directions are consistent with the regional principal compressive stress directions, which gradually varied from NE to NNW from north to south. The NE and WNW or NW faults also have a great influence on the directions of principal compressive stress. The polarization directions of fast shear-waves at stations near the strike-slip faults are parallel to the fault strikes, and a part of these shear-wave polarization directions are nearly perpendicular to the fault strikes, which are similar with the regional principal compressive stress directions. Several stations exhibit complex features, reflecting the complexity of tectonic environment in the study area. The delay times of slow shear-waves in the south part are higher than the north part, reflecting that the southern section has a greater degree of anisotropy in crust and the tectonic deformation is more intense. Compared with the upper mantle anisotropy of the North-South seismic zone, it is inferred that there may exist a complicated crust-mantle coupling phenomenon inside of the Sichuan-Yunnan rhombic block. The shear-wave splitting in the crust can not only reflect the regional stress characteristics, but also can reveal the regional tectonic information.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2017年第6期2181-2199,共19页
Chinese Journal of Geophysics
基金
国家自然科学基金(41474032)
"深地资源勘探开采"重点专项(2016YFC0600302)
地震预测研究所基本科研业务费专项(2016IES0304)共同资助
关键词
南北地震带
地壳各向异性
剪切波分裂
快波偏振方向
慢波时间延迟
构造
区域主压应力方向
South-north seismic zone Seismic anisotropy Shear-wave splitting Polarization of fast shear-wave Slow shear-wave time delay Tectonic Regional principal compressive stress direction
