中国东北地下结构背景噪声伴随层析成像

发布时间：2018-01-28 01:39

  本文关键词： 中国东北 经验格林函数 伴随层析 低波速通道 部分熔融 新生代火山活动　出处：《中国地质大学(北京)》2017年博士论文　论文类型：学位论文

【摘要】：中国东北部地区,地处两块重要克拉通之间,南接华北克拉通,北临西伯利亚克拉通,区域东边是日本海。该地区有着复杂的构造历史,其基底是一些复合陆块增生拼合形成的。在经过了古亚洲洋和蒙古-鄂霍茨克洋闭合后,.东北地区又经历了一系列的造山运动,盆地形成和火山活动,现在该地区已演变成由多种构造,包括造山带,盆地,断裂带和火山复合的区域。新生代火山活动广泛分布在研究区域内,特别是沿着盆地边缘的山谷和山地带发育,这使该区域成为了解板块内火山活动,和地幔过渡带内俯冲大洋板块与上覆构造结构相互作用的重要区域。通过使用背景噪声伴随层析方法,我们对中国东北地区的地壳及上地幔顶层构建了新的剪切波三维速度模型。与传统的背景噪声层析成像不同,我们的方法避免了反演过程中对相速度频散的获取和拟合,可以直接通过模型反演实际速度结构,减小了中间步骤造成的误差。通过对127个中国东北扩展地震台站(Northeast China Extended Seismic Array)两年的连续噪声数据进行互相关,我们得到了瑞利波经验格林函数(Empirical Green's functions),并选取6 - 40s频段的数据进行反演。研究的初始模型来自传统噪声层析成像方法的结果,通过伴随层析成像法多次反复迭代,使四个周期:6 - 15s,10 - 20s,15 - 30s和20 - 40s波段中测量的合成格林函数(Synthetic Green's functions)和原始数据EGFs之间的频率相关走时残差逐渐达到最小化,此时所得到的的模型即为我们所需的东北地区地壳的新三维剪切波速模型。我们的新模型显示出的剪切波速度异常分布,与已知的大地构造单元,如大兴安岭和长白山等,在空间分布上相互关联。此外,我们伴随层析法由于考虑了有限频率和三维传播效应,得到的成像结果表现出更明显的连续速度异常,并且异常幅度增大。我们的新模型还揭示了在中、下地壳和上地幔顶端存在着低速通道,这些低速异常表明哈拉哈,锡林浩特-阿巴嘎和镜泊湖火山下存在着部分熔融现象,暗示着该地区新一代火山活动的成分可能来源于更深层的地幔。
[Abstract]:Northeast China, located between two important cratons, is bounded by the North China Craton to the south, the Siberian Craton to the north, and the Sea of Japan to the east. The region has a complicated tectonic history. The basement was formed by the accretion and assemblage of some complex continental blocks. After the closure of the Paleo-Asian Ocean and Mongolia-Okhotsk Ocean, the northeast area experienced a series of orogenic movements, basin formation and volcanic activities. Now the area has evolved into an area of multiple structures, including orogenic belts, basins, fault zones and volcanoes. Cenozoic volcanic activity is widely distributed in the study area. In particular, valleys and mountain zones along the margin of the basin develop, which makes the region an understanding of intraplate volcanic activity. And an important area where the subduction ocean plate interacts with the overlying tectonic structure in the mantle transition zone by using the background noise accompanies tomography method. A new 3D velocity model of shear wave is constructed for the crust and upper mantle top of northeast China, which is different from the traditional background noise tomography. Our method avoids the acquisition and fitting of phase velocity dispersion in the inversion process, and can directly inversion the actual velocity structure through the model. The errors caused by the intermediate steps are reduced. The past China Extended Seismic Arrayvia 127 extended seismic stations in Northeast China are studied. The continuous noise data for two years are correlated with each other. We obtain empirical Green's functions of Rayleigh wave. The initial model is derived from the results of the traditional noise tomography method and iterated repeatedly by the accompanying tomography method. Make four cycles: 6-15 sm 10-20 s. Synthetic Green's functions measured in the bands 15-30s and 20-40s. The frequency dependent travel time residuals between EGFs and the original data are minimized gradually. The obtained model is a new 3D shear wave velocity model of the crust in Northeast China, which shows the anomalous distribution of shear wave velocity and the known tectonic units. For example, the Daxing'an Mountains and Changbai Mountains are interrelated in spatial distribution. In addition, due to the consideration of finite frequency and three-dimensional propagation effect, the imaging results show more obvious continuous velocity anomalies. Our new model also reveals the existence of low velocity channels at the top of the middle, lower crust and upper mantle, indicating that the low-velocity anomalies indicate Haraha. The presence of partial melting in the subvolcanoes of Xilinhot-Abaga and Jingpo Lake suggests that the composition of the new generation of volcanic activity in the region may originate from the deeper mantle.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P631.4;P542
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本文编号：1469402