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地震层析成像是随着反演理论的发展、计算机技术的进步等而发展起来的一种较新的地球物理方法。在过去的二十几年里，该方法不断进步，并广泛地应用到许多领域，尤其是在对地球内部结构的研究中，应用较广泛。 本文详细介绍了地震层析成像的原理和相关的几个技术，比如，模型参数化方法、射线追踪方法、速度反演方法、反演结果的评价等。 青藏高原地区的地壳上地幔速度结构对于研究高原的隆升机制与动力学过程具有重要意义。本文使用赵大鹏教授的层析成像程序来研究青藏高原地区的地壳上地幔速度结构。共使用262个流动和固定台站记录的15630个地震事件的233008条远震P波射线，反演得到了青藏高原地区较清晰的速度结构。 通过综合分析本文的层析成像结果并结合前人的研究成果，本文的结论主要包括： 1、青藏高原地区的速度异常多以高低速相间分布，异常的条带分隔、成带延伸特征明显。认为高速异常代表俯冲的印度板块或俯冲的大洋岩石圈的残块，低速异常与印度板块俯冲引起的扰动作用有关。 2、经度剖面大体刻画了青藏高原地区主要的地体边界，尤其是较清晰地展示了印度板块的俯冲形态。大部分地区的俯冲从北纬26度附近开始，并已越过北纬30度，部分地区已越过北纬32度。 3、青藏高原的东西向构造差异主要体现在速度异常分布的深度不同，在西部地区异常埋深较浅，而在东部地区异常埋深较深，速度异常以东倾展布。青藏高原中部发育两个近北北东向低速异常，它们与印度板块的俯冲有关。 4、俯冲的印度板块本身存在东西向差异。印度板块的俯冲及其自身的差异影响了青藏高原地区地壳上地幔的速度结构。 5、提出了在东经88度剖面，从北纬30度左右开始发育的北倾的高速异常，并对其进行了详细讨论，认为是俯冲的大洋岩石圈残片或俯冲的印度板块被分离的一部分。

Seismic tomography is a new geophysical method driven by developments of inversion theory and advances in computing. During the last two decades, many achievements about seismic tomography were obtained and this method has been widely used in a lot of fields, especially in the studying of the interior of the earth. This paper introduces the theory and method of seismic tomography in detail, for example, the method of model parameterization, ray tracing method, inversion method and the evaluation of the inversion results, etc. The crust and upper mantle structure beneath Tibet is very important for studying the uplift mechanism and the geodynamic processes of the plateau. We use 233008 rays from 15630 distant events recorded at 262 stations to perform teleseismic P wave tomography using the tomography program developed by Prof. Dapeng Zhao to study the 3-D seismic velocity structure of the crust and upper mantle beneath Tibet. The velocity structure of this region is obtained. Through comprehensive analysis on the inversion results and by the reference to other results, the major conclusions of this study on the 3-D velocity structure of the Tibetan Plateau are summarized as follows: 1 .the anomaly distribution in the Tibetan Plateau is characterized by the banded shape and the alternating high and low velocities. The high velocity anomalies are interpreted as a subducted Indian plate or the slab remnants of the oceanic lithosphere, while the low velocity anomalies are associated with the disturbing of the Indian plate subduction. 2. the major block boundaries are clearly shown in the profiles along longitude and the shapes of the subducted Indian plate are revealed clearly too. In most areas, the subduction begins at 26 degree north latitude and extends northward to 30 degree north latitude, reaching the depth of 400km or so. In some other areas the subducion extends northward to 32 degree north latitude. 3. the tectonic difference in east-west direction in the Tibetan Plateau is characterized by the different depths of the velocity anomalies. In general, the velocity anomaly distributions in the western part of the plateau are shallower than those in the eastern part. The anomalies dip eastward. There exist two low velocity anomalies in the middle part of the Tibetan Plateau which are related to the subduction of the Indian plate. 4. there exist manifest tectonic differences in east-west direction in the Indian plate. The differences and the subduction of the plate affect the crust and upper mantle velocity structure of the Tibetan Plateau. 5. the high velocity anomaly starting at about 30 degree north latitude along the profile of 88 degree east longitude is put forward and discussed in detail. The anomaly is interpreted as a slab remnant of the oceanic lithosphere or the upper layer of the delaminated Indian plate.

摘 要...........................................................................................................1
Abstract......................................................................................................2
引 言...........................................................................................................6
第一章 地震层析成像的基本理论........................................................9
第一节 地震层析成像的理论基础.......................................................................................9
一、Radon 变换...............................................................................................................9
二、射线理论的应用.....................................................................................................10
第二节 模型参数化.............................................................................................................12
第三节 射线追踪和走时计算.............................................................................................14
第四节 速度结构和震源参数的耦合问题.........................................................................19
第五节 速度反演.................................................................................................................20
一、Lanczos 过程..........................................................................................................20
二、LSQR 算法.............................................................................................................22
三、其他反演算法.........................................................................................................27
第六节 解的评价.................................................................................................................27
一、解的分辨率.............................................................................................................27
二、解的稳定性.............................................................................................................28
第二章 青藏高原岩石圈结构研究进展..............................................29
第一节 青藏高原的构造背景.............................................................................................29
一、喜马拉雅地体.........................................................................................................29
二、拉萨地体.................................................................................................................30
三、羌塘地体.................................................................................................................30
四、松潘－甘孜－可可西里地体.................................................................................31
五、东昆仑－柴达木地体.............................................................................................31
六、祁连山地体.............................................................................................................31
七、西昆仑山和喀喇昆仑山脉.....................................................................................31
第二节 青藏高原岩石圈结构地球物理探测进展.............................................................32
第三节 对青藏高原岩石圈结构的认识.............................................................................33
一、对地壳的认识.........................................................................................................33
二、对岩石圈地幔的认识.............................................................................................35
三、层析成像等的成果.................................................................................................36
四、青藏高原形成与隆升机制.....................................................................................37
第三章 青藏高原远震层析成像..........................................................39
第一节 数据及模型.............................................................................................................39
第二节 分辨率测试.............................................................................................................42
第三节 层析成像纵剖面结果.............................................................................................47
一、经度剖面(83°E～91°E) ..........................................................................................47
二、纬度剖面(26°N～33°N) .........................................................................................51
第四节 层析成像横剖面结果.............................................................................................52
一、25km 和45km.........................................................................................................52
二、70km 和100km.......................................................................................................52
三、175km 和220km.....................................................................................................52
四、270km、330km 和400km......................................................................................53
第五节 88°E 剖面高速异常带的讨论................................................................................57
一、88°E 相关剖面的成像比较....................................................................................58
二、88°E 剖面的地震学论证........................................................................................62
第四章 结论及其他..............................................................................65
第一节 对地震层析成像的体会及认识.............................................................................65
一、层析成像技术.........................................................................................................65
二、层析切片的解译.....................................................................................................65
三、层析成像的分辨率问题.........................................................................................65
四、青藏高原的岩石圈结构探测.................................................................................66
第二节 对本文层析成像结果的总体认识.........................................................................66
一、层析成像的特征.....................................................................................................66
二、印度板块的俯冲.....................................................................................................67
三、青藏高原的东西差异.............................................................................................67
第三节 本文存在的不足.....................................................................................................67
参考文献...................................................................................................69
发表论文...................................................................................................78
致 谢.........................................................................................................79