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Subject: 地球科学::地球物理学
Title: 藏南裂谷地区壳内P波速度结构与界面起伏特征
Author: 杨磊
Issued Date: 2009
Supervisor: 刘宏兵 ; 赵俊猛
Major: 固体地球物理学
Degree Grantor: 中国科学院研究生院
Place of Degree Grantor: 北京
Degree Level: 硕士
Keyword: 藏南裂谷 ;  走时反演 ;  速度结构 ;  壳内界面
Call Number: S000024
Department: 图书馆
Abstract: 本文是在对藏南地区人工地震宽角反射/折射数据的重新处理与解释的基础上撰写而成。首先详细介绍了射线理论的部分内容,即运动方程近似为标量波动方程、标量波动方程近似为射线程函方程以及费马定理,并以此为基础系统介绍了模型速度和界面可同时反演的二维地震走时反演算法(ZS92),阐述了其中的模型参数化方法,射线追踪的具体过程和走时反演。然后,运用ZS92重新处理了佩枯错-普莫雍错人工地震剖面,该剖面自西向东分别穿过藏南申扎-定结和尼玛-定日裂谷,获得了该剖面的界面起伏和速度结构。结果显示,在裂谷穿过的定日、定结附近壳内界面均有上隆的趋势,并且中、下地壳介质的速度较高,地壳内低速度层有明显的错断。尼玛-定日裂谷与申扎-定结裂谷有明显的深部背景。结合地震分布特点推测,软流圈的物质上涌,促使中上地壳部分物质熔融,熔融区地壳厚度减薄,产生应力集中,在张应力作用下形伸展构造。根据剖面附近的震源分布、地震发生的频率、剖面的速度结构与界面起伏之间的关系进一步推测藏南地区南北向裂谷的伸展活动仍在继续,并根据裂谷切割的规模和高原的构造的不均一性认为高原的东西向差异主要是由裂谷作用造成的。
English Abstract: This thesis is based on the reprocessing and interpretation of the refraction\reflection seismic data in the southern part of the Tibetan Plateau. First, parts of the ray theory, which contains scalar wave equation approximating to equation of particle motion, eikonal equation approximating to scalar equation, and Fernat’s theorem, are discussed in details in this thesis. On basis of the discussions, the algorithm of ZS92 (Zelt et al., 1992) is introduced systematically, which can determine the structure of 2-D velocity and interfaces simultaneously, including model parameterization, ray tracing and travetime inversion, and is then used in this thesis to reprocess the data of Peikuco-Pumoyingcuo seismic profile which goes across the Nima-Dingri rift and Shenzha-Dingjie rift from west to East. The P-wave velocity structure and the interfaces feature beneath the line are gained. The interfaces in the crust near Dingri and Dingjie which are loacated at Rifts have a tendency to uplift, and the related velocity in middle and lower crust is high. Low velocity layer in the middle crust has an offset. The formation of the Nima-Dingri rift and Shenzha-Dingjie rift contains deep background reasons. Compared with the distribution of the earthquakes in this region, it is speculated that the uplift of asthenosphere’s material causes partial melting in the crust, thus the thickness of crust in this area becomes thin, causing stress concentration, which lead to extensional tectonics under tensile stress. According to the features of the velocity and interface and the earthquake distribution, we further infer that the activity of the extensional tectonics is still on, and on basis of the rifts’ cutting scale and the differences of the deep structure of Tibetan Plateau, it is considered that the differences of structures in E-W direction are mainly caused by the rifting.
Language: 中文
Content Type: 学位论文
URI: http://ir.itpcas.ac.cn/handle/131C11/1217
Appears in Collections:图书馆_学位论文

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Recommended Citation:
杨磊.藏南裂谷地区壳内P波速度结构与界面起伏特征[硕士].北京.中国科学院研究生院.2009
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