【作者】 范俊喜；

【导师】 马瑾；

【作者基本信息】 中国地震局地质研究所 ， 构造地质学， 2002， 博士

【摘要】 中国大陆构造的成块性与中国大陆地震活动的成组性构成中国地震构造和地震活动的一个突出现象。论文研究了两者之间的联系，论证了地震活动的成组性与地质构造的成块性的关系，划分了地块活动类型。研究地块的运动特征是认识地震活动规律的关键问题之一。考虑到鄂尔多斯地块是中国大陆一个典型地块，地块内部构造简单，周缘则是著名的强震活动带，本文以之为例加以研究。利用地质、地形变和震源机制解资料对鄂尔多斯地块的运动过程进行了详细解析，发现鄂尔多斯地块的活动表现为整体性运动，其不同方向边界带的活动存在着交替性，从而建立了1000年来鄂尔多斯地块的运动动态过程，并用数值方法模拟了鄂尔多斯地块的运动和周边构造应力场。 一、中国大陆地质构造的成块性与地震活动的成组性 在前人对中国大陆地震成组划分的结果和地块划分方案的基础上，研究了中国大陆地块与成组地震活动之间的关系。发现大部分强震分布于地块边界断层上，成组地震的孕育和发生与块体活动有关。由成组地震震中分布图表现出来的地块活动方式主要有如下四种类型：①单缝式(相邻地块)活动型(A)，一组强震分布于两个相邻地块或两个相邻组合地块的共同边界上，表现为一组地震震中沿地块或地块组之间的一条缝分布。其中组合地块是指多个地块在某一时空范围内结合形成的一个统一地块，它在该时期控制了成组地震的发生。②单地块活动型(B)：一组强震分布于一个地块或一个组合地块的周边，可能与某一地块或组合地块的运动(平移、旋转、掀斜及其组合形式)有关。③多地块活动型(C)，一组地震分布于若干地块各自的边界上，表现为多个地块同时活动。④地块内部活动型(D)，一组地震分布于一个或多个地块的内部，表现为地块内部构造活动。每种地块活动类型出现的频次并不相同，在考虑了非成组地震时，地块活动频度以单缝式活动型为最高；单就成组地震而言，地块活动主要以单块式活动型为主。另一方面大陆内部各地块的活动性也有差别，仅就涉及到成组地震的频次而言，东部比较活跃的地块有太行山地块和华北平原地块，西部比较活跃的地块有川滇和昆仑-松潘地块。 二、鄂尔多斯地块运动的整体性与不同方向边界带活动的交替活性 从以下几个方面研究了鄂尔多斯地块的运动特点。①从地质资料分析，鄂尔多斯地块除西南缘为弧形挤压断裂外，其周边围绕着一系列断陷盆地带，盆地外侧为山地。反映鄂尔多斯地块主要处于伸展构造环境中。由各盆地的走向和排列方式，可知地块南北、东西两侧边界分别为左旋、右旋走滑剪切拉张带，两者形成一对共轭剪切拉张带。根据各断陷带内断裂活动特征，地块南北两侧主要以拉张断陷为主，东西两侧则以走滑运动为主，东西边界的活动比南北边界强。②从地震活动性分析，若以鄂尔多斯地块周边各个断陷带为单元，其地震活跃期和平静期长短不一，无明显规律，但是把鄂尔多斯地块周边断陷带作为一个整体，其地震活动则呈现出约300年活动期，100年平静期的明显规律，表明鄂尔多斯地区的地震活动不是以断陷带为活动单元，而是以地块为活动单元。这一方面说明鄂尔多斯地块的整体性，另一方面也表明地块活动决定着其周边强震的孕育与发生；地震活动性还呈现出另一规律，地块的南北边界带与东边界带的构造活动是交替发生的。③从地形变资料分析，近几年来GPS观测结果显示哪尔多斯及其周边地块相对稳定的欧亚大陆在向南东东方向运动，各地块的运动速度存在着差别，引起了地块之间的构造运动和变形.本文根据w如g学等(2加l)的结果拟合了部尔多斯及周边地块的运动速度，求出了周边各地块相对部尔多斯地块的运动速度，分别投影到相应的断陷边界带的延伸方向和其垂直方向上。由此得到，在GPS施测期间周边断陷带的运动方式总体上同长期内地质平均结果相似，即南北、东西边界断陷带分别为左旋、右旋剪切拉张，西南缘为挤压边界，略带左旋运动.但也显示出一些与地质结果相矛盾的现象:地块南北边界，即渭河断陷带和河套断陷带的走滑分量显著，而东西边界，即山西断陷带和银川断陷带的拉张分量显著，这与各边界带长时期运动的地质结果不符，反映出地块南北边界带正处于构造活动时期。七十年代到八十年代末的精密水准资料反映出那尔多斯地块与太行山地块之间存在着微挤压隆起，也不同于近几年该带上的拉张运动。多期精密水准网资料还反映出哪尔多斯地块与周边地块间的相互作用存在着周期性的加强与减弱现象。 总之，邵尔多斯地块运动的整体性表现为:在地块内部无活动构造分布;地震活动以地块为单元;地块内部的GPS侧点间差异运动较小;垂直形变零等值线沿地块边界分布。部尔多斯地块不同方向边界活动的交替性表现为:在南北边界带与东西边界带上的地震活跃期存在明显的交替活动现象，·反映出两带构造活动的交替性;近期GPS结果反映的地块南北边界带较大的走滑运动，而东西边界带走滑运动很小，主要为拉张运动，与长期地质结果不符，从而说明两者在不同时期交替地成为地块的主导活动边界带。各种资料表明至少从八十年代末期以来，鄂尔多斯地块南北边界带处于构造活动时期;近几年?更多还原

【Abstract】 The China continent can be divided into several tectonic blocks by nearly NE- and EW-trending faults. Meanwhile strong earthquakes in the China continent usually cluster in time and space. The relationship between these two major features of the China continent is studied in this thesis, and several types of block motions are identified based on grouping of earthquakes. It is one of the key problems for understanding seismicity to study block motions. The Ordos Block is a typical block which has simple interior structures, and active seismicity around it So the Ordos block is taken as the target of the case study for mis work. The results show that the Odors Block is moving as a whole body. When the faults along the northern and southern boundaries of the Ordos block are active, its eastern boundary is inactive. However, if the faults along the eastern boundary are active, the northern and southern are inactive. The motion process of the Ordos Block since last 1000 years is also analysed in the thesis. And the motions of the Ordos block and the stress field around it are modeling with the numerial method.1 Block motions and Grouping of earthquakes in the China continentThis work attempts to find out corresponding relation between tectonic blocks and earthquakes in groups that were identified by previous studies. It has been found that most of earthquake groups are associated with block boundaries. Four types of block movement are identified based on relations between epicenters and blocks.(1) Movement along the single boundary of a block (or between two neighboring blocks) (A): Earthquakes in a group occur between two blocks, and epicenters in a group distribute along the single boundary of a block (neighboring blocks) or a combined block. A combined block refers to two or more blocks that are combined as one unit in some extent of time and space which controls where and how earthquakes occur. (2) Movement of a single block (a combined block) (B): Earthquakes in a group occur around a block or a combined block. This type can be associated with motions (slips, rotation, tilt, or compound movement) of a block or a combined block. (3) Movement of multi-blocks (C): Earthquakes in a group occur around two or more blocks. It demonstrates that blocks are active in the same time. (4) Movement in block interiors (D): Earthquakes in a group occur in the interior of a block. Isolated earthquakes other than earthquakes in groups mentioned above are called earthquakes of non-grouping. If we consider isolated earthquakes as earthquakes in groups which include only one earthquake, all types of block movement identified with isolated earthquakes are movement along a single boundary of a block (or combined blocks). The frequency of each type is different. If earthquakes of non-grouping are counted, the movement along a single boundary of a block (or combined blocks) is popular in four types, but movement of a single block dominates in modes if grouping earthquakes are only counted. Activity of blocks is also different from each other. Based on the block’s frequencies related to earthquake groups, it is counted that the Taihangshan Mountain and the North China block are most active in eastern China, and theChuandian and the Kunlun-Songpan block are most active in western China.2 The Ordos Block moveing as a whole body and alternative activity of boundaries around itThe study about the Ordos block motions includes following aspects. (1) Geological data indicate that the graben basins around the Ordos block where the Loess Plateau is located, represent major extentional tectonic features since late Cenozoic time in north China, except some thrusts along the southwestern margin of the block. The extension dominates in this region. The kinematics of graben systems indicates that the regions along the northern and southern margins of the Ordos are left-lateral extension belts, and the western and eastern margins of the Ordos are right-lateral extension belts. The kinematics of the faults shows that normal faults are更多还原