本文選題：可控源電磁法 + 三維正演　； 參考：《吉林大學》2015年碩士論文

【摘要】：可控源音頻大地電磁測深(CSAMT)自上世紀七十年代以來，已經不斷發(fā)展為一種重要的電磁法勘探手段并得到廣泛的應用。隨著CSAMT法的理論發(fā)展，及電磁勘探儀器方面的研究方面的進步，對數(shù)據(jù)處理方法和解釋均提出了更高的要求，迫切地需求三維數(shù)據(jù)的采集以及精確有效的數(shù)據(jù)處理方法，針對這一現(xiàn)狀，本文對理論數(shù)據(jù)進行三維數(shù)值模擬并進行有限內存擬牛頓法反演，然后結合可控源電磁勘探實際數(shù)據(jù)進行研究。 本文利用交錯網格有限差分法對可控源音頻大地電磁法的理論數(shù)據(jù)進行三維正演。對于層狀背景模型中存在低阻異常體和高阻異常體的情況的電場分布特點進行了分析和總結。 反演方面，采用的是有限內存BFGS法(L-BFGS)。該方法是擬牛頓法的一種，不需要存儲大型海森矩陣或它的逆矩陣，只需存儲前面m次的迭代信息，從而減小了反演時占用的計算機空間。利用有限內存BFGS法對文中正演部分的理論模型計算結果，通過給出不同的反演初始背景電阻率對不同頻率的數(shù)據(jù)進行反演，并對結果進行分析。反演結果說明，該方法對于理論數(shù)據(jù)可以準確反映異常體的電阻率高低、位置、形態(tài)的信息，證明了有限內存擬牛頓法對進行三維可控源頻率測深數(shù)據(jù)反演的可行性。 最后，本文對實測的可控源數(shù)據(jù)進行了反演模擬。將實測數(shù)據(jù)編輯之后進行反演，為了計算方便，，選擇單個頻率進行反演。從實際數(shù)據(jù)的反演結果中可以看出，由于實際地質情況更加復雜，只能根據(jù)反演的電阻率分布情況判斷地下結構，而反演的電阻率數(shù)值不夠精確，因此需要在實際數(shù)據(jù)的反演方面進行更加全面和深入的研究。 本文通過對理論模型和實際數(shù)據(jù)正反演計算分析得出以下結論： （1）利用有限差分交錯網格法對理論模型進行正演，對計算結果進行對比分析可以總結出不同地質條件下電場的響應規(guī)律，通過對響應規(guī)律的總結可以為反演工作提供思路和參考； （2） L-BFGS法三維反演在理論模型中的應用說明，選擇合適的反演參數(shù)，該方法可以比較準確的反映出異常體的位置形態(tài)及電阻率的高低，擬合差下降速度快，模型數(shù)據(jù)收斂明顯； （3）對實測數(shù)據(jù)進行了L-BFGS法三維反演。實際數(shù)據(jù)反演結果中高阻低阻區(qū)分明顯，可以根據(jù)電阻率的分布情況判斷地下地質構造情況。
[Abstract]:Since the 1970s, the controllable source audio magnetotelluric sounding (CSAMT) has been developed as an important method of electromagnetic exploration and has been widely used. With the development of the theory of CSAMT method and the progress of the research on electromagnetic exploration instruments, the data processing method and interpretation are required to be higher, and the 3D data acquisition and accurate and effective data processing methods are urgently needed. In view of this situation, this paper carries on the three-dimensional numerical simulation to the theoretical data and carries on the finite memory quasi Newton method inversion, then unifies the controllable source electromagnetic exploration actual data to carry on the research. In this paper, the staggered grid finite difference method is used to forward the theoretical data of controllable source audio magnetotelluric method. The characteristics of electric field distribution in the case of low resistivity anomaly and high resistivity anomaly in layered background model are analyzed and summarized. In inversion, the finite memory BFGS method is used. This method is a quasi-Newton method, which does not need to store large Heyson matrix or its inverse matrix, but only needs to store the information of the previous m iterations, thus reducing the computer space used in inversion. The finite memory BFGS method is used to calculate the theoretical model of the forward part of the paper. The data of different frequencies are inversed by different inversion background resistivity, and the results are analyzed. The inversion results show that the method can accurately reflect the information of resistivity, position and shape for theoretical data, and proves the feasibility of the finite memory quasi-Newton method for inversion of 3-D controllable source frequency sounding data. Finally, the inversion simulation of the measured controllable source data is carried out. After editing the measured data, the inversion is carried out, and for the convenience of calculation, a single frequency is selected for inversion. From the inversion results of the actual data, it can be seen that because the actual geological conditions are more complicated, the underground structure can only be judged according to the resistivity distribution of the inversion, but the inversion resistivity value is not accurate enough. Therefore, more comprehensive and in-depth research on the inversion of actual data is needed. In this paper, the following conclusions are drawn through the analysis of the theoretical model and the actual data forward and inverse calculation. 1) by using the finite difference staggered grid method to forward the theoretical model, the response law of electric field under different geological conditions can be summed up by comparing and analyzing the calculated results. Through the summary of the response law, we can provide ideas and references for the inversion work. 2) the application of L-BFGS method in theoretical model shows that by selecting appropriate inversion parameters, this method can accurately reflect the position shape and resistivity of abnormal body, and the falling speed of fitting difference is fast, and the convergence of model data is obvious. 3) three dimensional inversion of measured data by L-BFGS method is carried out. The difference between high resistivity and low resistivity is obvious in the inversion result of actual data, and the underground geological structure can be judged according to the distribution of resistivity.
【學位授予單位】：吉林大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P631.325

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