本文選題：大地電磁　切入點：極化分析　出處：《中國地質(zhì)大學(xué)(北京)》2015年碩士論文

【摘要】：20世紀(jì)90年代以來大地電磁測深法發(fā)展迅速,并被廣泛應(yīng)用于區(qū)域斷裂構(gòu)造、流體運動、板塊構(gòu)造以及大陸動力學(xué)等方面的研究中。在實測數(shù)據(jù)處理以及阻抗的計算和分析中,信號中的噪聲是一個不可忽視的問題。實踐證明,在工業(yè)區(qū)、市區(qū)和農(nóng)業(yè)區(qū)附近采集的大地電磁時間序列極易受到人文噪聲的干擾。為獲得穩(wěn)定可靠的阻抗估計,檢測和分離人文噪聲便成為了現(xiàn)代大地電磁法必須要解決的問題。多數(shù)人文噪聲源在空間屬性中對于大地電磁場來說是局部的,它所產(chǎn)生的電磁信號是在特定方向上線性極化的。與之相反,廣泛存在于自然界中的大地電磁場信號由于其場源的多樣性,所以理論上在天然場中觀測得到的大地電磁信號是非線性極化的。這就是極化分析應(yīng)用于大地電磁數(shù)據(jù)處理的基礎(chǔ)。論文首先基于地球物理小波庫,編寫MATLAB程序從而實現(xiàn)了極化分析算法。并利用此算法針對大地電磁信號中常見的幾種噪聲,研究了它們的極化屬性特征。其過程主要是：首先將大地電磁時間序列中常見的幾種噪聲添加到受干擾較少的實測數(shù)據(jù)中,進(jìn)行極化分析。然后選擇含有噪聲的多個實測數(shù)據(jù)段進(jìn)行極化分析。最后得到了脈沖干擾和矩形干擾等大地電磁信號中的典型噪聲的極化屬性特征。發(fā)現(xiàn)了脈沖干擾和矩形干擾往往會引起極化橢圓率的零值異常,在極化屬性圖中可以看到明顯的楔形零值區(qū)域；在相應(yīng)時頻區(qū)域內(nèi),引起極化角圍繞一個固定值變化的現(xiàn)象,相位差也會出現(xiàn)類似的現(xiàn)象。在橢圓率方面,脈沖干擾引起的楔形異常區(qū)域往往體現(xiàn)為“窄長”型,而矩形干擾引起的異常區(qū)往往表現(xiàn)為“矮寬”型。此后,進(jìn)一步根據(jù)這些噪聲的極化屬性特征(主要依靠極化橢圓率的特征)來對大地電磁時間序列中的脈沖干擾和矩形干擾進(jìn)行時域定位,并使用了大量的實測數(shù)據(jù)來驗證時域定位算法的可靠性。最后根據(jù)得到的噪聲時域位置以及噪聲存在類型,依次對相應(yīng)位置處的時頻譜進(jìn)行處理,繼而經(jīng)過小波反變換得到去除噪聲后的信號。通過大量實驗數(shù)據(jù)和實測數(shù)據(jù)的檢驗,證明了極化分析方法應(yīng)用在大地電磁實測數(shù)據(jù)中進(jìn)行噪聲定位及信噪分離的可行性。
[Abstract]:Magnetotelluric sounding has been developed rapidly since 1990s and has been widely used in the study of regional fault structure fluid movement plate tectonics and continental dynamics.In the calculation and analysis of the measured data and impedance, the noise in the signal is a problem that can not be ignored.It has been proved that magnetotelluric time series collected in industrial area, urban area and agricultural area are easily disturbed by human noise.In order to obtain stable and reliable impedance estimation, detection and separation of human noise has become a problem that must be solved in modern magnetotelluric method.Most of the human noise sources are local to the magnetotelluric field in their spatial properties, and the electromagnetic signals generated by them are linearly polarized in a particular direction.On the contrary, the magnetotelluric field signals widely existing in nature are nonlinear polarized because of the diversity of their field sources.This is the basis of polarization analysis applied to magnetotelluric data processing.Firstly, based on geophysical wavelet library, MATLAB program is written to realize polarization analysis algorithm.The polarization properties of magnetotelluric signals are studied by using this algorithm.The main process is as follows: firstly, some common noises in magnetotelluric time series are added to the measured data with less interference, and polarization analysis is carried out.Then, several real data segments with noise are selected for polarization analysis.Finally, the polarization properties of typical noises in magnetotelluric signals such as pulse interference and rectangular interference are obtained.It is found that pulse interference and rectangular interference often lead to zero anomaly of polarization ellipticity, and the wedge-shaped zero value region can be seen in the polarization attribute map, and the polarization angle changes around a fixed value in the corresponding time-frequency region.The phase difference will also appear similar phenomenon.In terms of ellipticity, the wedge-shaped anomaly caused by pulse interference is usually of "narrow length" type, while the anomalous region caused by rectangular interference is often characterized by "short width" type.Then, according to the polarimetric properties of these noises (which mainly depend on the characteristics of polarization ellipticity), the pulse interference and rectangular interference in magnetotelluric time series are located in time domain.A large number of measured data are used to verify the reliability of the time domain localization algorithm.Finally, according to the noise time domain position and the noise existence type, the time spectrum at the corresponding position is processed in turn, and then the signal after removing noise is obtained by wavelet inverse transform.The feasibility of using polarization analysis method to locate noise and separate signal and noise in magnetotelluric data is proved by testing a large number of experimental data and measured data.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P631.325

【參考文獻(xiàn)】

相關(guān)期刊論文 前4條

1 陳文超,師振盛,汪文秉,高靜懷;小波變換在去除探地雷達(dá)信號直達(dá)波的應(yīng)用[J];電波科學(xué)學(xué)報;2000年03期

2 魏文博;我國大地電磁測深新進(jìn)展及瞻望[J];地球物理學(xué)進(jìn)展;2002年02期

3 湯井田;李晉;肖曉;張林成;呂慶田;;數(shù)學(xué)形態(tài)濾波與大地電磁噪聲壓制[J];地球物理學(xué)報;2012年05期

4 孫潔,晉光文,白登海,梁竟閣,王立鳳;大地電磁測深資料的噪聲干擾[J];物探與化探;2000年02期

，

本文編號：1714040