本文關(guān)鍵詞： 數(shù)據(jù)空間 共軛梯度(CG) 二維反演 大地電磁法　出處：《東華理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：大地電磁測(cè)深法(MT)是以天然電磁場(chǎng)為場(chǎng)源,通過(guò)觀測(cè)相互正交的電場(chǎng)和磁場(chǎng)分量并計(jì)算卡尼亞視電阻率和相位來(lái)研究和解決地質(zhì)問(wèn)題的一種頻率域電磁法。國(guó)內(nèi)外地球物理工作者已提出了多種反演方法,并在實(shí)際應(yīng)用中取得良好效果,但對(duì)已有方法的改進(jìn)優(yōu)化和新方法的探索研究從未停止。本文首先利用有限差分法實(shí)現(xiàn)TE和TM模式下的二維大地電磁正演,并通過(guò)典型地電模型驗(yàn)證了算法的準(zhǔn)確性和適用性。然后開(kāi)展了基于數(shù)據(jù)空間的共軛梯度反演算法實(shí)現(xiàn)大地電磁二維反演研究。該算法是在OCCAM反演算法基礎(chǔ)上利用共軛梯度算法求解模型更新算子,由于從模型空間M轉(zhuǎn)換到數(shù)據(jù)空間N內(nèi)計(jì)算,極大減小了計(jì)算內(nèi)存和運(yùn)行量,另外只需計(jì)算JACOBI矩陣或矩陣轉(zhuǎn)置與向量的乘積,避免JACOBI矩陣直接存儲(chǔ)和計(jì)算。利用開(kāi)發(fā)的基于數(shù)據(jù)空間的共軛梯度反演算法,試算了幾個(gè)典型地電模型,通過(guò)與非線性共軛梯度反演算法(NLCG)對(duì)比表明:DCG反演算法具有NLCG算法相同準(zhǔn)確性,且具有收斂速度更快和縱向分辨率更高的優(yōu)勢(shì)。論文還開(kāi)展噪聲水平、初始模型、正則化因子等反演參數(shù)研究,結(jié)果表明正則化因子采用“L”曲線法選取較好,該反演方法具有較強(qiáng)抗噪能力、對(duì)初始模型依賴性較小、適應(yīng)性強(qiáng)等特點(diǎn)。因此本文開(kāi)發(fā)的基于數(shù)據(jù)空間的MT二維共軛梯度反演算法是一種穩(wěn)定、可靠的反演算法,為大地電磁實(shí)際數(shù)據(jù)資料解釋和三維反演研究提供新途徑。
[Abstract]:Magnetotelluric sounding (MT) is a natural electromagnetic field source. A frequency-domain electromagnetic method for studying and solving geological problems by observing the components of electric and magnetic fields which are orthogonal to each other and calculating Kania apparent resistivity and phase. Many inversion methods have been proposed by geophysicians at home and abroad. Good results have been obtained in practical application, but the improvement and optimization of existing methods and the exploration of new methods have never stopped. Firstly, the finite difference method is used to realize two-dimensional magnetotelluric forward modeling in te and TM modes. The accuracy and applicability of the algorithm are verified by typical geoelectric model. Then, the conjugate gradient inversion algorithm based on data space is developed to realize two-dimensional inversion of magnetotelluric. The algorithm is based on OCCAM inversion algorithm. The conjugate gradient algorithm is used to solve the model update operator. Because of the transformation from the model space M to the data space N calculation, the computational memory and the running amount are greatly reduced, and the JACOBI matrix or matrix transpose and vector product are only calculated. To avoid the direct storage and calculation of JACOBI matrix, several typical geoelectric models are calculated by using the developed conjugate gradient inversion algorithm based on data space. The comparison with the nonlinear conjugate gradient inversion algorithm shows that the NLCG algorithm has the same accuracy. And it has the advantage of faster convergence speed and higher vertical resolution. The paper also studies the inversion parameters such as noise level, initial model, regularization factor and so on. The results show that the regularization factor is better selected by "L" curve method, the inversion method has strong anti-noise ability and has less dependence on the initial model. Therefore the MT 2D conjugate gradient inversion algorithm based on data space developed in this paper is a stable and reliable inversion algorithm. It provides a new way for the interpretation of magnetotelluric data and the study of 3D inversion.
【學(xué)位授予單位】：東華理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P631.325

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相關(guān)期刊論文 前2條

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本文編號(hào)：1488966