【作者】 张广成；

【导师】 吴庆举；

【作者基本信息】 中国地震局地球物理研究所 ， 固体地球物理学， 2012， 博士

【摘要】 中国东北地区位于兴蒙造山带的东部,南接华北克拉通,东临西北太平洋边缘海,作为太平洋俯冲的弧后地区,不仅深源地震频发,也是火山活动最强烈的地区之一,是研究太平洋俯冲带动力学的理想观测场所。本文简要介绍了近年来东北地区地壳上地幔结构以及西北太平洋俯冲带取得的研究成果,对比层析成像,三重震相等与转换波成像的异同,并用接收函数方法进一步研究了东北地区的地壳各向异性和地壳上地幔结构。本文用在东北地区布设的两条密集台站长剖面的116个台站2009年至2011年记录的远震数据,和研究区内国家和区域台网的123个固定台同期记录的数据,提取接收函数并进Ps震相的分裂分析,H-K扫描叠加和CCP叠加,获得了该区的地壳各向异性信息,地壳厚度和泊松比分布情况以及上地幔过渡带受西北太平洋板块俯冲的影响情况,初步探讨了东北地区深部动力学模式。本文的研究表明：1)东北地区地壳介质各向异性快波与慢波的时间延迟约为0.15～0.3秒,较SKS/SKKS各向异性快慢波时间延迟小。大多数的台站下方地壳各向异性快波偏振方向显示为北西向,与张应力方向和板块运动方向一致,推测该区地壳应力场总体表现为拉张应力为主。而小部分位于断裂构造附近或者大兴安岭褶皱带中的台站显示快波偏振方向为北东向,反映了该区地壳介质应力区域复杂性。通过与SKS/SKKS各向异性对比,在大兴安岭地区快波偏振方向与其基本一致,暗示了地壳各向异性来自下地壳,也反映了该区壳幔垂直变形一致性。2)东北地区地壳厚度总体表现为东西两边厚,中间薄的格局。大兴安岭及其以西的高原地区和东部佳木斯地块地壳厚度较厚,大约在36-42km之间；中部的松辽盆地,小兴安岭槽地地块,胶辽台隆,燕山台隆东端,下辽河盆地等地地壳厚度较薄,厚度在29-36km左右。泊松比值总体偏高,大兴安岭褶皱带,松辽盆地,长白山山脉沿线,泊松比值在0.25以上。泊松比值较高暗示此处或是存在熔融(长白山),或是地幔物质底侵作用影响下地壳,使其铁镁组分增加(松辽盆地)。这些地区往往地热流值比周围高。莫霍在该区重力梯度带以西较平缓,起伏不大。受到深大断裂嫩江断裂,依兰-伊通断裂和敦化-密山断裂的影响,莫霍界面出现起伏变化。尤其是在敦化-密山断裂附近,莫霍界面出现明显错断,推断与太平洋俯冲板块挤压有关。3)410km和660km间断面均出现了大范围的下沉。410km间断面下沉约10km,660km间断面下沉10～30km左右。过渡带厚度在松辽盆地变小,推测松辽盆地下方有地幔物质上涌。660km在依兰-伊通断裂下方出现不止一个界面,推测俯冲板片到达此位置附近,使得其前方的地幔物质向上扰动影响了松辽盆地。更多还原

【Abstract】 Northeastern China is located east of Xingmeng orogen, north of the North China Craton, west of Pacific Sea. As a back-arc region of subduction of the Pacific, not only deep earthquakes frequently occered, but also one of the most intense areas of volcanism, is the ideal place to study the dynamics of the Pacific subduction.Firstly, we introduced the results of the crust and upper mantle structure study and northwest Pacific subduction in the recent years in the northeastern China. We compare the receiver function results with the tomography, triplicate waveform and do the further study about crust anositropy and crust and upper mantle structure by receiver functions.We use teleseismic data recorded by116temporary stations and121national earthquake network stations located in NE China to calculate the receiver functions and got the crust anositropy by auto mative shear-wave splitting program, and also get information of crustal thickness and Poisson’s ratio by H-K stacking. We also use CCP stacking method to map the topography of the upper mantle discontinuities and do some preliminary investigation with the deep dynamic model of northeastern China.Results are summarized in the fllowing.l)The delay time between fast wave and slow wave of the crust anositropy in the northeastern China is about0.15-0.3%秒. It is much smaller than the time delay of SKS/SKKS anositropy. The crust beneath most stations show the fast wave polarization direction is nearly northwest, the same direction as the tensile stress and the movement of the plate. We infer that the main stress of the crust is tensile stress. But also a few stations located near the fault and Greater Khingan Mountains show a different fast wave direction which is northeast. This mean the crustal anositropy is regional and complexity. By the compareation with SKS/SKKS in the same area, the crustal fast wave polarization is almost the same as it of the SKS/SKKS. And this means the anositropy is come from the under crust, and this reflect that the consistency of the crust and mantle vertical deformation.2) The overral performance of the crustal thickness of the northeastern China is eastern and western thicker than the central. The crustal thickness beneath Greater Khingan Mountains, Hulunberer Plateau and Jiamusi massif are much chicker, about36-42km. In the Songliao Basin, Lesser Khingan Range trough fold belt, Jiaoliao uplift, east of Yanshan bold belt and south Liaohe Basin the crustal thickness is thin, and it is between29km and36km. The Poisson Ratio in the study area is a little higher, such as it in the Greater Khingan mountains bold belt, Songliao Basin, Changbai mountains the Poisson Ratio is larger than0.25. the high value of Poisson Ratio means that beneath this region maybe exist melting(Changbai Mountain) or upwelling make the under crust contains much Fe and Mg elements. The heat flow in this region is always higher than around. The Moho is flat in the west of the gravity lineament. With the influence of the deep faults which named Nenjiang faults, Yilan-Yitong faults and Dunhua-Mishan faults, the Moho becomes up and down in some region. Especially near the Dunhua-Mishan faults, the Moho shows a clear dislocation, we infer it has a close relationship with the Pacific slab subduction.3) Both the410km and660km discontinuities express a wide range of sinking. The410km discontinuity about sinks10km and the660km sinks10-30km. We infer there exists upwellings beneath the Songliao Basin from the thickness of the upper mantle transition zone become thinner. There are several interfaces near the660km in Yilan-Yitong faults, it is suggested that the subduction slab reached near this location and making the mantle materials upwelling and make a seriously influence on the Songliao Basin.更多还原