解析訊號與尤拉解迴旋方法的發展與應用

Development and applications of analytic signal and Euler deconvolution methods

杜文斌(Wen-Bin Doo)

指導教授 ： 許樹坤

國立中央大學/地球科學學院/地球物理研究所/博士(2011年)

摘要

磁力與重力資料經常用來研究和探討地質構造上的特性，其中大部份的應用是要找到地下構造的位置。為了達成這個目的，資料分析的方法就成為很重要的一環，其中解析訊號與尤拉解迴旋方法是廣為大家所使用的方法，使用這兩種方法的主要好處是它可以在不受到地磁場其他未知參數的影響之下求得地下物質的深度、位置及幾何形貌。本研究中以解析訊號及尤拉解迴旋方法為主要基礎，進一步發展出新的方法並討論其應用。
首先結合解析訊號與尤拉解迴旋方法來計算二維磁源參數，如此，地下構造的位置、深度、構造指標、磁化強度差及構造傾角等參數可經由此新方法的計算得知。另外可藉由此方法來計算地磁反轉邊界因地磁場變化而產生的磁化強度差。有了反轉邊界磁化強度差的資訊，在做磁力定年模擬時，磁化層在不同年代就不用給定相同的磁化強度，這可使得計算結果更符合真實狀況。本論文以Brunhes-Matuyama地磁場反轉邊界為例來探討此想法的可行性。
泊松理論在重力與磁力位間提供了一個簡單的關係式，在這關係式下磁化強度與密度的比值可以被求得。在此論文中，我們將泊松關系式加入了解析訊號的應用，則磁化強度與密度的比值可以直接利用重力與磁力資料求得，而不需要經由逆推方法計算地下物質的密度及磁化強度。經由計算所得之磁化強度與密度比值的分佈可作為我們區分地下岩性時的參考依據。將此方法應用在台灣北部外海區域，比對在此區域內的反射震測剖面結果，發現此方法可以辨識出在棉花嶼及彭佳嶼區域較深部的火成物體。
最後，本論文實際探討2009年莫拉克颱風在台灣南部引發了土石流，而掩蓋了小林村大部分的建築物的探測。論文中分析在土石流發生後所收集的磁力資料，經由比對災前建築物的位置與研究區域內磁力資料分析的結果，可得知高解析磁力探測可以有效地解析被掩埋建築物的位置，而磁力資料計算所得的可能建築物埋深約5-10公尺。另外由磁力資料分析結果可推測在小林村北邊的建築物幾乎都被沖毀，而在南邊的建築物則大部分都還保留在原地，藉此結果也可推測土石流的方向可能是N250°。

關鍵字

解析訊號 ； 尤拉解迴旋

並列摘要

Magnetic and gravity data are generally used to discuss geological structure characteristics, and the most applications are used to determine the location of the sources. Among the interpretation techniques, the methods of the analytic signal and Euler deconvolution have been widely adopted for these purposes. The major advantage of using these two techniques is that the determination of magnetic source locations and depths is independent of the ambient earth magnetic parameters. In this thesis, generally based on the analytic signal and Euler deconvolution we attempt to develop new methods and then discuss its applications.
We have developed a new method by using the joint analysis of analytic signal and Euler deconvolution to estimate the parameters of 2D magnetic sources, especially to identify the horizontal locations, depths, structural types (indices), magnetization contrasts and structural dips. Furthermore, this method is used to estimate the possible magnetization contrast of geomagnetic reversals. This information could be a useful constrain for geomagnetic age modeling. Thus, one does not need to assume a constant magnetization of the magnetized layer in the modeling. This could make the synthetic magnetic anomaly more realistic. This method has been tested to determine the magnetization contrast of the Brunhes-Matuyama boundary of geomagnetic reversal.
The Poisson theorem provides a simple relationship between the gravity and magnetic potentials. Based on the simple Poisson theorem, magnetization/density ratio (MDR) can be estimated. Here, we combined the Poisson theorem and analytic signal technique to estimate MDR. Follow this method the MDR values can be determined from gravity and magnetic data. Apply this method to a profile across the offshore area of the northern Taiwan. In comparison with the reflection seismic profile, it shows that the method can help us to identify the existence of a deep-seated igneous body beneath the area of Mienhuayu and Pengchiagu islands off northern Taiwan.
Finally, we show a magnetic survey result for the purpose of detecting buried buildings of Siaolin Village in southern Taiwan after the catastrophic landslide induced by Typhoon Morakot in 2009. Compared the original locations of buildings with the magnetic data analysis results, high-resolution magnetic survey can effectively identify positions of buried buildings in Siaolin Village. The estimated depths of the possible buried buildings are about 5-10 meters deep. In addition, magnetic data analysis can further suggest the possible debris-flow direction of N250o, because the northern part of village was mostly destroyed off while the southern part of village buildings remained in place.

並列關鍵字

Euler deconvolution ； analytic signal

參考文獻

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