台灣地區地下磁性構造研究;The study of the subsurface magnetic structure in Taiwan

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题名:	台灣地區地下磁性構造研究;The study of the subsurface magnetic structure in Taiwan
作者:	陳俊榕;Chen, Chun-Rong
贡献者:	地球科學學系
关键词:	全島普測;磁力異常;磁感率;火成岩;geomagnetic;susceptibility;igneous rock
日期:	2018-03-28
上传时间:	2018-04-13 11:01:35 (UTC+8)
出版者:	國立中央大學
摘要:	本研究利用台灣全島磁力普測的磁力異常資料推求地下磁性構造。為嘗試解決磁力逆推計算上長久以來遇到的「非唯一解」問題，結合速度構造與磁性構造進行轉換，以期得到一符合速度與磁感率兩種不同物理性質的結果。使用不同礦岩所具有的速度特性，進行分類與給定磁感率而得一符合速度構造之磁感率模型。轉換而得的磁感率模型做為逆推中參考模型使用。磁力普測的磁力異常資料，經過測點資料重新網格化為5 km * 5 km後進行三維逆推計算。經過三維逆推計算後得到台灣第一個完整且包覆全島的地下磁感率模型。本研究另又利用Magnetic Vector Inversion(MVI)方法分析台灣地區地下磁性構造的分布。藉由綜合逆推計算感應磁化強度與非感應磁化強度，更能反映地下磁性構造的真實情形。比較兩種不同的逆推方法，並選擇較適合台灣的逆推磁感率模型。逆推結果顯示，台灣地區地下磁感率高區分佈位置大多與正磁力異常高值相符合。磁感率高區大致上與火成岩相關，由北至南包含了大屯火山區的岩漿庫、公館及角板山期的火山活動、雲彰古陸向本島的延伸、海岸山脈火山島弧的火成岩或是中央山脈下方高溫的地震稀少帶，都反映了磁感率高區與火成岩的關係。;This study used the island-wide magnetic prospection data to calculate the subsurface magnetic structures in Taiwan. In order to face the difficulty that the uncertainty is often a challenge when underlying structural models are constructed using unitary geophysical data retrieved from field prospections. The velocity-susceptibility model is obtained by given the susceptibility to specific mineral/rock which is determined by the velocity characteristics. Then, the velocity-susceptibility model is imported as a reference model during the 3-D inversion calculation. The magnetic anomaly data are reprocessed into 5 km x 5 km x 5 km grid data to calculate the subsurface susceptibility model in Taiwan. Another inversion method “Magnetic Vector Inversion” (MVI) method is used in this study. This method combines two magnetizations, induction magnetization and non-induction magnetization, in to the calculation. Therefore, the result will better conform to reality that the igneous rock usually has remanence. Compared the results of the two methods and find out which is suitable for discussing the magnetic structure in Taiwan. The result shows that most of the high susceptibility areas are fitting with the area haveing high positive magnetic anomaly. High susceptibility are roughly agreed with the existence of igneous rock such as the magma chamber of Tatun Volcano Group, the eruption of volcano during Gongguan and Jiaobanshan series, the Yun-Chang Paleo-High from the Penghu ridge, the volcanic arc in the eastern Taiwan and the aseismicity region in the southern Central mountain range. The calculation results are comparable to the known structures in Taiwan.
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