松潘甘孜及邻区构造变形特征及其数值模拟

【作者】 张燕；

【导师】 程顺有；

【作者基本信息】 西北大学 ， 构造地质学， 2006， 硕士

【摘要】 构造活动和变形与地壳运动密切相关,是各种地球动力学过程在地表的综合显现,是地壳介质对板块构造和深部动力过程的综合响应,因此对地壳运动和变形的研究构成地球动力学研究的重要内容。传统上一般用地质学的构造解析法进行研究,只能解决情况简单小范围的地质构造变形,而要研究大尺度构造变形与动力学机制必须借助于数值模拟方法。 文中首先归纳总结了研究区及四周的深部结构特征、构造变形特征及地壳现今运动GPS测量结果。对研究区内夏河一龙日坝剖面的深部结构也进行了二度半重力反演拟合,认为深部存在多个低速层,厚度并不均匀。 简要介绍了弹性力学问题中有限元数值分析方法的基本思想和一般过程。以GPS观测结果为边界约束,结合其它地质地球物理资料,得到三维地壳模型,利用有限元分析软件ANSYS模拟了松潘甘孜及邻区的地壳运动位移场,应力、应变场。进一步模拟分析了玛沁-靖边地震剖面上的应力应变场。将数值模拟结果与其它观测研究结果作了较全面的对比,其吻合程度较好,表明模型及计算结果是合理和可靠的。 在计算结果基础上,对研究区现今构造应力场及构造变形特征进行了初步分析探讨。研究区应力场格局基本上是稳定的,以北东向主应力为主,在东部发生偏转。各块体的位移量从南向北逐渐减小,方向总体为北东方向,这暗示了各区块的构造变形是受到现今应力场控制而形成的,而印度板块向北东俯冲是研究区现今应力场、构造变形形成演化的主导动力。更多还原

【Abstract】 The movement and deformation of the crust are the comprehensive effects of various kinds of the geodynamical processes on the ground, and the systematical response of the crustal medium to the plate tectonic and deeply dynamic evolution. Therefore, the research for them becomes one of important contents in the geodynamic studies. The characteristics of the movement and deformation of the crust were traditional determined with the geological and seismographic methods which can solve the deformation of the crust structure for simple shape and small range. As a result, it is necessary to employ numerical simulation to in vestigate the deformation of the crust for large scale and geodynamical processes.At first, the characteristics of the depth structure and deformation of the crust tectonics are described and analysed in this thesis. The Global Positioning System (GPS) measurements of current movement are generalized and analysed well. Two half-dimensional simulation of gravity anomaly at Xiahe-Longriba profile shows that there are several low velocity body, which depth are not equality.The principles of the finite-element method and the general process of the finite-element analysis in the elastic mechanics are simple. introduced at first in this thesis. The finite-element software, called the ANSYS, is used to simulate the displacement, stress and strain fields of the crustal movement in the Song Pan GanZi and its near region with the boundary constraint of the GPS observations combining with other geologic and geophysics results.The model is three-dimensions. Moreover, the stress and strain fields were simulate of the section of Maqing-Jingbian. The numerical results obtained in this study are closed accordance with the other corresponding results obtained by some authors. It implies that the model and the numerical results are reasonable and reliable.Based on the numerical results, the present characteristics of the tectonic stress field in the Song Pan GanZi and its near region are primarily discussed in this thesis. From the figure of the simulated stress field, it is found that the stress pattern is steady ,as a whole . The north-east compressive stress is dominant in this regions, the direction of the compressivestress chang to north-east-east near the east of region. The displacement of blocks reduce from south to north block. The direction of the movement is north-east in this region. It is suggested that the structure deformation in SongPan GanZi and its near region is a result of the control of the current stress fields. The dominant force that are generated by combined actions of the Indian and Eurasia plate collision lead to the cunent stress fields and the structure deformation.更多还原