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对布设在鄂尔多斯块体及周缘的固定和流动宽频带地震台网共111个台站记录作远震SKS(SKKS)波形资料偏振分析,采用最小切向能量的网格搜索和叠加分析求得每一个台站的SKS(SKKS)快波偏振方向和快、慢波的延迟时间,获得了鄂尔多斯块体及周缘上地幔各向异性图像.在鄂尔多斯块体西缘和北缘,各向异性的快波方向为NW-SE方向,一致性较好;在鄂尔多斯多斯块体南缘,快波方向主要是NWW-SEE和近EW方向;在鄂尔多斯块体东缘,快波方向总体表现为近EW方向,间有NEE-SWW方向和NWW-SEE方向.在鄂尔多斯块体内部,快波方向在北部是近NS方向,而南部则是近EW方向.快、慢波的时间延迟范围是0.48～1.50s,鄂尔多斯块体内部的时间延迟平均值小于其周缘地区.通过分析研究区各向异性特征,认为构造稳定的鄂尔多斯块体内部的各向异性主要来自于古老的华北克拉通保存的“化石”各向异性;青藏高原东北缘向NE方向的推挤,造成岩石圈NW-SE方向的拉张伸展,鄂尔多斯块体西缘和北缘下的上地幔物质沿NW-SE方向发生了形变,使得上地幔中橄榄岩的晶格排列方向平行于物质形变的方向;在鄂尔多斯块体南缘,刚性的华北块体和扬子块体碰撞作用,使得各向异性快波方向平行于两个刚性块体的碰撞边界和秦岭造山带的走向.结合该区域绝对板块运动和速度结构研究,认为在秦岭造山带下可能存在一个青藏高原物质东流的地幔流通道;在鄂尔多斯块体东缘的汾河地堑和太行山,相对复杂的各向异性特征可能由于西太平板块俯冲、区域伸展构造、造山运动等共同作用引起的.对于YCI台得到的各向异性参数(快波方向变化范围是45°～106°,时间延迟变化范围是0.6～1.5s)随事件反方位角呈现出π/2周期的变化,符合双层各向异性模型.基于0.125Hz的主频和实测的各向异性参数,我们模拟得到了最佳的双层各向异性模型,下层φlower=132°,δtlower=0.8s,上层φupper=83°,δtupper=0.5s.上层各向异性归功于古老克拉通保留的“化石”各向异性,下层各向异性则受到了青藏高原东北缘NE方向推挤导致的岩石圈NW-SE方向的拉张伸展作用.通过该区域各向异性快波方向与全球定位系统(GPS)的观测结果的对比分析,鄂尔多斯块体的周缘壳幔变形符合垂直连贯变形模式,而其内部变形复杂,有待进一步研究.
A total of 111 station records of fixed and mobile broadband seismic networks deployed in the Ordos block and its periphery were used for polarimetric analysis of SKKS waveform data. The grid search and overlay analysis of minimum tangential energy The anisotropy of Ordos block and its upper mantle was obtained by fast wave polarization and fast and slow wave delay of SKS (SKKS) station in a station. The direction of NW-SE wave direction is better, and the fast wave direction is mainly NWW-SEE and near EW direction in the southern margin of Ordos block. In the eastern edge of Ordos block, the fast wave direction is generally near EW Direction, with NEE-SWW direction and NWW-SEE direction.In the Ordos block, the fast-wave direction is near-NS in the north and near-EW in the south.The time delay of fast and slow waves ranges from 0.48 to 1.50 s, the average time delay in the Ordos block is smaller than that in the peripheral area.By analyzing the anisotropy of the study area, it is considered that the anisotropy in the stable Erdos block mainly comes from the ancient “preserved fossils of the North China Craton ”Anisotropy; The northeastern margin of the Tibetan Plateau pushed in the NE direction resulted in the extension and extension of the NW-SE lithosphere. The upper mantle beneath the western margin and the northern margin of the Ordos block deformed along the NW-SE so that the upper mantle olives The lattice orientation of the rock is parallel to the direction of material deformation. In the southern margin of Ordos block, the collision between the rigid North China block and the Yangtze block makes the anisotropic fast wave direction parallel to the collision boundary of two rigid blocks and Based on the study of the absolute plate movement and velocity structure in this area, it is considered that there may exist a mantle flow channel eastward of the Qinghai-Tibet Plateau under the Qinling orogenic belt, that the Fenhe graben and the Taihang Mountains in the eastern Ordos block, The relatively complex anisotropy characteristics may be caused by the interaction of the western Pacific plate subduction, regional extensional structure and orogeny, etc. For the anisotropic parameters obtained from YCI station (the range of the fast wave direction is 45 ° -106 °, the time delay The variation range is 0.6 ~ 1.5s), the π / 2 period changes with the anti-azimuth of the event, which accords with the bilayer anisotropy model.According to the dominant frequency of 0.125Hz and the measured anisotropy parameters, The best two-layer anisotropy models were simulated, with lower φlower = 132 °, δlower = 0.8s, upper φupper = 83 °, and δtupper = 0.5s. The upper anisotropy is attributed to the “fossil remains” "Anisotropy, the lower anisotropy is affected by the NE direction of the northeastern margin of the Qinghai-Tibet Plateau, which leads to NW-SE lithospheric stretching and stretching. Through the anisotropic fast-wave direction in this region and the global positioning system (GPS ), The crust-mantle deformation of the Ordos block accords with the vertically coherent deformation mode, and its internal deformation is complex and awaits further study.