本文選題：大地電磁 + 三維響應(yīng)��； 參考：《成都理工大學(xué)》2017年碩士論文

【摘要】：實(shí)際的地電構(gòu)造是三維的,故應(yīng)在大地電磁中采取三維的反演方法來得到地下的電性結(jié)構(gòu),但現(xiàn)在大地電磁三維的反演因?yàn)榇嬖谝恍﹩栴}而仍未得到廣泛使用。故研究大地電磁三維響應(yīng)的二維反演解釋是較有意義的。本文首先介紹分析大地電磁三維正演基本的一些理論和公式、三維響應(yīng)特征,然后簡要介紹了二維反演的一些基本理論和公式并對(duì)比介紹了不同二維反演方法的特點(diǎn)及其在不同極化模式下的特征;其后對(duì)大地電磁的阻抗張量進(jìn)行了理解和學(xué)習(xí),重點(diǎn)學(xué)習(xí)了相位張量分解的特點(diǎn)和用法;然后建立了一個(gè)三維空間中存在不同電阻率塊體的典型三維模型,以分析其在不同極化模式下的三維響應(yīng)特征,深刻研究其特征差異,即不同極化模式對(duì)電性分界面分辨的靈敏度,并探究了其原因;建立了另外一個(gè)空間中存在一個(gè)低阻塊體的三維模型,以分析其在不同極化模式下的二維反演結(jié)果,探究了極化模式的選擇對(duì)二維反演的影響;最后綜合利用上述的研究成果對(duì)兩個(gè)較復(fù)雜的模型進(jìn)行了試算,采取阻抗相位張量分解,進(jìn)行構(gòu)造維性分析、尋求最佳旋轉(zhuǎn)角,并將旋轉(zhuǎn)后的數(shù)據(jù)作二維反演,探求了一種大地電磁資料處理解釋的合理流程。發(fā)現(xiàn)對(duì)于同一異常體,不同極化模式的正演響應(yīng)是不一樣的,其不同極化模式的反演結(jié)果也會(huì)出現(xiàn)一些差異,有時(shí)差異較大,也就是說不同的極化模式對(duì)電性分界面的分辨能力是不一樣的;在野外工作,布設(shè)測線時(shí),應(yīng)當(dāng)盡量垂直于構(gòu)造的走向,并且采取合適的極化模式來進(jìn)行反演。并且對(duì)于三維響應(yīng)尤其是實(shí)測資料很容易出現(xiàn)受淺表低阻體等影響而引起畸變的情況,或者遇到采樣方向不與構(gòu)造走向垂直的情況,假設(shè)不對(duì)觀測資料進(jìn)行任何的校正,而直接做反演解釋,那么所得到的結(jié)果將會(huì)出現(xiàn)偏離實(shí)際構(gòu)造的情況;另外,假如采用的校正方法不恰當(dāng)?shù)脑?也會(huì)使得后續(xù)的反演結(jié)果得到錯(cuò)誤的結(jié)論;故應(yīng)首先選取合適的地球物理模型、張量分解方式,進(jìn)行阻抗張量分解、構(gòu)造維性分析、求取最佳旋轉(zhuǎn)角,并將數(shù)據(jù)旋轉(zhuǎn)到最佳角度,再進(jìn)行合適極化模式的二維反演,最終將可能消除冗余構(gòu)造、達(dá)到合理的反演效果。
[Abstract]:The actual geoelectric structure is three-dimensional, so the three-dimensional inversion method should be adopted in magnetotelluric to obtain the underground electrical structure, but the magnetotelluric three-dimensional inversion is still not widely used because of some problems. So it is meaningful to study the two-dimensional inversion interpretation of magnetotelluric response. This paper first introduces some basic theories and formulas for the analysis of magnetotelluric three-dimensional forward modeling, and the three-dimensional response characteristics. Then, some basic theories and formulas of two-dimensional inversion are briefly introduced, the characteristics of different two-dimensional inversion methods and their characteristics under different polarization modes are compared, and then the impedance Zhang Liang of magnetotelluric is understood and studied. The characteristics and usage of phase Zhang Liang decomposition are studied emphatically, and then a typical three-dimensional model with different resistivity blocks in three dimensional space is established to analyze the three-dimensional response characteristics of different polarization modes and to study the difference of their characteristics. That is, the sensitivity of different polarization modes to the resolution of electrically separated interfaces, and the reasons for the resolution, and the establishment of a three-dimensional model with a low resistivity block in another space to analyze the two-dimensional inversion results under different polarization modes. The influence of the choice of polarization mode on two-dimensional inversion is explored. Finally, two more complex models are calculated by synthetically using the above research results. The structural dimension is analyzed by using impedance phase Zhang Liang decomposition, and the optimum rotation angle is obtained. A reasonable flow of magnetotelluric data processing and interpretation is obtained by using two dimensional inversion of the rotated data. It is found that for the same anomalous body, the forward response of different polarization models is different, and the inversion results of different polarization models will be different, sometimes quite different. In other words, different polarization modes have different ability to distinguish the electric boundary surface, and in the field work, the line should be perpendicular to the strike of the structure, and the appropriate polarization mode should be adopted to carry on the inversion. It is also assumed that the 3-D response, especially the observed data, is easily distorted by shallow low resistivity, or that the sampling direction is not perpendicular to the direction of the structure, assuming that no correction is made to the observed data. In addition, if the correction method is not appropriate, it will make the subsequent inversion result get the wrong conclusion, and the inversion result will deviate from the actual structure directly, and if the correction method is not appropriate, it will make the subsequent inversion result get the wrong conclusion. Therefore, it is necessary to select the appropriate geophysical model, Zhang Liang decomposition method, impedance Zhang Liang decomposition, construct dimension analysis, obtain the best rotation angle, rotate the data to the best angle, and then carry out the two-dimensional inversion of the appropriate polarization model. In the end, redundant structures will be eliminated and reasonable inversion results will be achieved.
【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P631.325

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