【作者】 徐权辉；

【导师】 王绪本；

【作者基本信息】 成都理工大学 ， 地球探测与信息技术， 2009， 硕士

【摘要】 本文采用新型的超长周期大地电磁测深仪LEMT417与V8多功能电法仪相结合,在龙门山前山断裂带进行宽频带超长周期大地电磁观测,并且采用先进的大地电磁资料处理与解释技术,对龙门山前山断裂带剖面进行分析,研究得到较为可信的龙门山前山断裂带深部电性结构,总结前人的工作成果,发挥大地电磁测深的优势,针对龙门山断裂带的一些热点问题进行了探讨和研究。文章首先介绍了龙门山前山冲断带剖面的工作情况,该剖面南起雅安天全,北至广元,全长500km;回顾了龙门山地区的研究历史和大地电磁测深的发展历程,结合超长周期仪器工作的特点,在断裂带沿线位置布置工作点,总共完成测深点12个,每个测深点均同步完成了常规大地电磁测深仪(即V8多功能电法仪)与超长周期大地电磁测深仪(即LEMT417)的采集工作,并且简单介绍了超长周期资料处理流程,对两套仪器的数据进行了科学的拼接与处理,得到了宽频带的大地电磁测深资料。对于剖面资料进行定性分析和解释是本文的重点之一。通过张量阻抗的旋转得到剖面最佳电性主轴方向,在北段和中段最佳主轴方向为北西向,而在南段则偏转为北东向;利用Mohr圆分析和极化图分析方法,对所有12个测点进行分析,得到了二维偏离角和各向异性角,结论是剖面整体表现二维性,而在断裂分段区域各向异性程度和三维性较强;阻抗二维偏离度也得到类似的结论;通过对实测视电阻率和相位曲线类型和断面图特征进行研究分析,了解了主要构造的电性特点,为剖面的电性解释提供了基础。在研究两套仪器特点的基础上,对比两套仪器在同一测点所得实测视电阻率曲线,对数据进行衔接和调整,得到可信的宽频带大地电磁测深曲线;在反演模式的选择上,总结了前人的宝贵经验,介绍了反演方法的发展现状和一维反演的基本原理,简单介绍MTsoft2D V2.1软件的使用流程,最后选择BOSTICK2D反演方法和TE+TM联合的模式反演进行反演,得到了剖面宽频带的反演结果。最后,以龙门山地区研究历史为背景,介绍了研究区主要的地层分布、断裂构造等地质情况,详细说明了研究区的具体研究背景,并结合定性分析结果,分析了剖面电性结构,揭示了龙门山逆冲推覆构造的存在。更多还原

【Abstract】 In this paper, combining a new type of ultra-long period magnetotelluric sounding instrument LEMT417 with multifunction instrument V8 to carry out the broad-band ultra-long period for magnetotelluric observation in outlying Longmen mountain fault zone, and use of advanced data processing and interpretation of electromagnetic technology to analyses outlying Longmen mountain fault profile, which has gained very credible outlying Longmen mountain deep fault electrical structure, and summed up the results of previous work. At the same time, the Longmen mountain fracture with a number of hot issues were discussed and researched according to the advantage of magnetotelluric sounding.The paper firstly introduces the work of the outlying Longmen mountain thrust belt profile. And the profile is from the south to the north that is from Tianquan, Ya’an to Guangyuan, which total length is 500km.Then reviewing the study history of Longmen mountain and the development course of magnetotelluric sounding, combining with ultra– long period instrument characteristics, lay outing the work point the location of along the fault zone, and the paper briefly introduces the process of ultra– long period data processing.Qualitative analysis and interpretation of profile information is one of the key points of this paper. The best direction of electrical axis are achieved by rotating tensor impedance, the best main axis direction is North West - South East in the northern section and the middle section ,but is deflected to North East - West in the southern section; using of Mohr circle analysis and polarization diagrams analysis for all 12 measuring points, to get the deviation angle and anisotropic two-dimensional angle, and the conclusion is that the overall performance of the profile is two-dimensional , and anisotropy and three-dimensional is very strong in sub-region of the fracture; similar conclusion is also reached in two-dimensional impedance deviation; The electrical characteristics of the main structure is understood provides the basis for interpretation by the analysis and the study of the measured apparent resistivity, the type of phase curves and characteristics of cross-section.Based on studying characteristics of two instruments, comparing the measured apparent resistivity curve of two instruments from the same measuring point, and carrying out convergence and adjustment of data, is to be credible broadband magnetotelluric sounding curve; to the choice of model in the inversion, summed up the valuable experience of those predecessors, the paper introduces the development of inversion and the basic principle of one-dimensional inversion, briefly presents MTsoft2D V2.1 software processes .At last inversion method OCCAM1D and TE + TM joint inversion model inversion were chose, which has gained the inversion results of wide-band profile.Finally, in the background of the history of Longmen Mountain, the paper introduces the distribution of major stratigraphic, geological faults, etc. in the study area, and combining the results of qualitative analysis, reveals the existence of the Longmen mountain thrust and analyses the structure of electrical section.更多还原