本文選題：大地電磁測深　切入點：靜態(tài)效應　出處：《吉林大學》2015年碩士論文　論文類型：學位論文

【摘要】：大地電磁測深法利用天然交變電磁場研究地球電性結構，不受高阻層屏蔽，，對低阻層分辨率高。無需人工建立場源，施工方便，成本低廉，勘探深度范圍大，在能源、資源及深部地球物理勘探等領域得到了廣泛的應用。 大地電磁測深法中存在一個普遍問題是數據中存在靜位移,亦即對數視電阻率-周期曲線相對于區(qū)域值有一個豎直方向上的平行移動。這些靜位移是由于測點附近存在小規(guī)模，淺部導電性異常體。電荷在小于電磁場趨膚深度的近地表異常體上積累。這些積累電荷在觀測電場區(qū)域值的基礎上產生了一個持續(xù)到任意低頻率的擾動。錯誤的移除這些局部失真會導致反演解釋所要研究的深部目標體時出現(xiàn)錯誤。 電磁測深法的數據解釋和靜態(tài)效應校正通常是分開處理的。對于同樣的實測數據不同的靜態(tài)校應校正方法可能會得到不同的靜位移值，這樣一來，先移除數據中的靜位移再尋找一個擬合被處理過的數據的模型就存在一個風險，這個風險就是地電結構推斷解釋中出現(xiàn)的異常可能是由于特定的靜位移選擇引起的。反演的同時校正靜態(tài)效應的方法則可避免這個風險。 在一維情況下，對含有靜位移的大地電磁測深數據做反演解釋所獲得的模型和基于未失真數據得到的模型可能有一致的結構，但視電阻率值和深度可能是錯誤的。在二維和三維情況下，每個測點靜位移的量通常是不一樣的，當試圖解釋含有靜態(tài)效應的數據時可能會導致所獲得的模型中出現(xiàn)多余的結構。在一些特殊情況下，甚至找不到擬合數據的模型。為了移除多余的粗糙度，可以在每個點引進兩個靜位移參數用于縮放每個點TE和TM兩種模式的視電阻率，但相位數據不受影響。Occam反演可以在獲得最光滑模型的同時移除靜態(tài)效應的影響。把靜位移當作自由的參數參與到光滑模型反演中可以保證反演結果中出現(xiàn)的異常不只是由錯誤的靜態(tài)效應校正引起的。 本文在對當前中外相關文獻收集和研讀的基礎上，對當前大地電磁測深資料處理中經常用到的靜態(tài)效應校正手段進行研究。對所建立的一些理論模型進行了正演模擬，得出近地表局部不均勻體位于不同地電模型中時，兩種模式(TE，TM)的響應特征。然后將靜位移作為一個反演參數直接參與反演，在反演過程中同時校正由地表局部不均勻體引起的靜態(tài)效應。結果表明，利用靜態(tài)效應的直接反演法來校正靜態(tài)效應可以獲得不錯的效果。 最后，用靜態(tài)效應的直接反演法處理了本溪-集安地區(qū)的實測大地電磁測深資料。有效的消除了實測數據中含有的靜態(tài)效應，使得反演解釋更加合理。
[Abstract]:The magnetotelluric sounding method uses natural alternating electromagnetic field to study the electrical structure of the earth, which is not shielded by the high resistivity layer, and has high resolution to the low resistivity layer. There is no need to establish the field source manually, the construction is convenient, the cost is low, the exploration depth range is large, and the exploration depth is in the energy source. Resources and deep geophysical exploration have been widely used. A common problem in magnetotelluric sounding is the existence of static displacement in the data. That is, the logarithmic apparent resistivity periodic curve has a vertical parallel movement relative to the regional value. These static displacements are due to the presence of small scales near the measured points. Shallow electrical conductivity anomaly. The charge accumulates on an anomaly near the surface that is smaller than the depth of the electromagnetic field. These accumulative charges produce a disturbance that persists to any low frequency on the basis of the observed electric field region. Removing these local distortions will lead to errors in the inversion interpretation of the deep object. Data interpretation and static effect correction of electromagnetic sounding methods are usually handled separately. Different static correction methods for the same measured data may result in different static displacement values. There is a risk of removing the static displacement from the data and then finding a model to fit the processed data. The risk is that the anomalies in the geoelectric structure inference interpretation may be caused by a particular static displacement selection, and this risk can be avoided by the method of inversion and correction of the static effect. In one dimensional case, the model derived from inversion interpretation of magnetotelluric sounding data with static displacement may have a consistent structure with the model based on undistorted data. But the apparent resistivity and depth can be wrong. In two and three dimensions, the amount of static displacement at each measuring point is usually different. When trying to interpret data with static effects, it may lead to redundant structures in the obtained model. In some special cases, no model can even be found to fit the data. In order to remove the excess roughness, Two static displacement parameters can be introduced at each point to scale the apparent resistivity of the te and TM modes at each point, But the phase data is unaffected. Occam inversion can remove the static effect while obtaining the smoothest model. Taking static displacement as a free parameter to participate in the smooth model inversion can ensure the anomalies in the inversion results. It is not just caused by incorrect static effect correction. In this paper, on the basis of the collection and study of the relevant literature at home and abroad, the static effect correction methods used frequently in the processing of magnetotelluric sounding data are studied, and the forward modeling of some theoretical models is carried out. The response characteristics of the two models in different geoelectric models are obtained, and the static displacement is taken as an inversion parameter to directly participate in the inversion. In the process of inversion, the static effects caused by local inhomogeneous bodies on the surface are corrected at the same time. The results show that the direct inversion method of static effects can get good results. Finally, the direct inversion method of static effect is used to deal with the measured magnetotelluric sounding data in Benxi-Ji'an area, which effectively eliminates the static effect in the measured data and makes the inversion interpretation more reasonable.
【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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