利用重力資料估算台灣海峽之莫霍面深度; Moho Depth Beneath the Taiwan Strait From Gravity Data

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Title:	利用重力資料估算台灣海峽之莫霍面深度;Moho Depth Beneath the Taiwan Strait From Gravity Data
Authors:	史旻弘;Min-Hung Shih
Contributors:	地球物理研究所
Keywords:	莫霍面;力資料;灣海峽;sinx/x;oho;aiwan Strait;ravity
Date:	2001-07-10
Issue Date:	2009-09-22 09:53:35 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	海峽地區之莫霍面深度變化，至今尚未有具有全面性的完整研究。因此，本研究係利用台灣海峽及其附近區域之重力資料，以sinx/x法估算台灣海峽之莫霍面深度。在研究中所使用之重力資料，取自台灣本島及其離島地區、福建省與台灣鄰近海域之重力資料，經過重新整理、編彙後再加以運用。本文中所使用之sinx/x法，係以Convolution Method處理重力資料，計算過程中所採用之濾波函數為，以去除較短波長的重力波。文中在台灣海峽地區由北而南，選取六條剖線加以計算。由於台灣海峽有巨厚之沉積層存在，因此針對沉積層造成之重力影響再加以修正。最後，推算出台灣海峽地區之莫霍面起伏情況。由本研究之結果得知，台灣海峽地區之地殼厚度約25-30公里，最薄的地區在台灣省彰化縣外海一帶，其厚度為23公里；最厚的區域位處南日島盆地附近，厚度為30公里。海峽地區之地殼起伏分布情況，大致呈中間淺薄，兩側較厚的趨勢。較淺薄的部分與台灣海峽中由北而南的構造高區相對應，地殼較厚的部分則反應出沉積盆地或凹陷地區之位置所在。而莫霍面的起伏，大致與地表之重力異常值變化，以及區域構造的位置呈正相關。又由於海峽地區所發生之地震，多屬深度在30公里以上之淺源地震，其震源位置集中分布在莫霍面以上。因此，海峽地區之地震的發生應與地殼之構造活動有關。 So far, there are scarce studies about the variation in the thickness of the earth’s crust in the Taiwan Strait. Therefore, we used the gravity data in Taiwan Strait and it’s surrounding by method of sinx/x to calculate the depth of the Moho-discontinuity. The gravity data were compiled of three parts: Taiwan island and it’s off-shore islands, Fujian Province﹐and the marine area around Taiwan island. To remove the shorter wavelength of gravity data, the convolution method (as the filter function sinx/x) is used to deal with the gravity data. In the study, we select six profiles across the Taiwan Strait. Furthermore, we consider about the gravity effects due to the thick layer of sediments in the Taiwan Strait. Eventually, we estimate the undulation of the Moho. The main results of this study are as follows: (1) the crustal thinkness beneath the Taiwan Strait is about 23-30 km; the thinnest area locates the off-shore nearby Changhua County with 23 km and the thickening toward the Nanjihtao Basin reaches up to 30 km; (2) the thickness decreases from Fujian Province to the central Taiwan Strait, and then increases to the Taiwan island; (3) the undulation of the Moho is related to the observed gravity anomaly and regional structure, such as structural high, sedimentary basin or depression; (4) Numerous earthquakes occurred in the Taiwan Strait belong to the shallower earthquakes, that is, the hypocenters concentrate above the Moho. Consequently, the earthquake occurred in the Taiwan Strait is caused by the crustal activities.
Appears in Collections:	[Graduate Institute of Geophysics] Electronic Thesis & Dissertation

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