應用 iTilt-Euler法探討澎湖西南外海 磁力異常構造;Apply iTilt-Euler method on the magnetic anomaly at southwest of Penghu.

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Title:	應用 iTilt-Euler法探討澎湖西南外海磁力異常構造;Apply iTilt-Euler method on the magnetic anomaly at southwest of Penghu.
Authors:	徐敬;HSU, CHING
Contributors:	地球科學學系
Keywords:	地磁;增強傾斜尤拉法;澎湖;Geomagnetic;Improved Tilt-Euler method;Penghu
Date:	2022-08-29
Issue Date:	2022-10-04 11:12:35 (UTC+8)
Publisher:	國立中央大學
Abstract:	在澎湖西南外海磁力資料中，大約位於(119.08∘E、23.46∘N)處有一磁力異常區，其最大磁力異常值約為620nT，而在其東方約6海浬處也有另一處較弱的磁力異常區(異常值約為340nT)，本研究希望透過磁力分析的方法來探討此兩處磁力異常區下方的異常構造。為了減少傳統尤拉解迴旋法中因為構造指標選取不準確而造成的置解發散的現象，本研究將會選用增強傾斜-尤拉法（improved Tilt-Euler method）作為主要計算方法。同時會計算前、中、後搭配自行設計的計算篩選流程，以期能提高計算結果的準確度。最後將會得到此兩處磁力異常區域下方構造位置、深度以及能夠代表其構造幾何意義的構造指標(structural index)。　　結果顯示：西側磁力異常區下方異常體深度約為0.7至0.9公里深，且平均構造指標為0.24的斷層構造。而東側異常區經計算後顯示該處構造深度約為1.8至1.9公里深，平均構造指標為1.4的岩脈構造。 ;While we check the magnetic data measured from New Ocean Reacher 3 on 2020/9/21-29, we can easily find that there are two anomalies located at southwest of Penghu. For the west one, it’s located about 〖119.08〗^° E,〖23.46〗^° N and with the anomaly amount about 620 nT. The other site is located at 〖119.34〗^∘ E , 〖23.45〗^∘ N but not strong as the first one (340 nT). To understand the magnetic structural under these two sites, this study will use the iTilt-Euler method being the main method to calculate the depth of these two magnetic anomalies. Before applying iTilt-Euler method, I’ll calculate total horizontal gradient and only use “quality of local maximum” larger than 3 to make sure the input data are around the edge of source. After iTilt-Euler method, we’ll use zero order analytic signal as a constraint to pick out the solutions which is above the structural. Final, I will use the average of those picked solutions represent the properties of this anomaly site. After the process, I found that, the structural of the west site might be the fault at 0.88 km depth with the average structural index 0.23, and the other site is the dike located at 1.8 km depth with structural index 1.4.
Appears in Collections:	[Graduate Institute of Geophysics] Electronic Thesis & Dissertation

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