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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/15215

Title: 台灣西南海域高屏峽谷西側天然氣水合物速度構造
Velocity-Interface Structure of Gas Hydrates West of Kaoping Canyon off SW Taiwan
Authors: Chih-Hsien Chen
陳志賢
Contributors: NTOU:Institute of Applied Geosciences
國立臺灣海洋大學:應用地球科學研究所
Keywords: 海底地震儀;海底仿擬反射;多頻道反射震測;天然氣水合物
OBS;BSR;MCS;Gas-Hydrate
Date: 2007
Issue Date: 2011-06-30T08:08:56Z
Abstract: 本研究結合2006年4月由海研一號793航次24頻道反射震測資料與海研三號1148航次海底地震儀之四分量折射與廣角反射震測資料探討高屏海底峽谷西側之天然氣水合物分布。從反射震測資料可發現位於海床反射訊號下方約0.3秒的海底仿擬反射(BSR)訊號以及其上層的反射訊號,因此可建立較正確的沉積層初始速度模型。本研究也充分使用海底地震儀的首波、折射波及反射波走時,並以波跡追蹤法與走時反演法建立天然氣水合物的P波速度-界面與泊松比模型。 根據海底地震儀震測P波速度模型,我們發現BSR上方水合物層的P波速度為1.8-2.04公里/秒,而其厚度則為100-150公尺;BSR下之游離氣層P波速度與厚度則減少為1.4-1.72公里/秒與30-110公尺。其中,在天然氣水合物地化特徵明顯的G-5A (OBS A4) 與G-N1 (OBS D21) 站南側地形高區之水合物層P波速度(2.04公里/秒)最高、游離氣層速度(1.4公里/秒)最低且速度變化最劇烈。我們認為由於基磐隆起而造成向南傾斜的逆衝斷層,而使游離氣沿著逆衝斷層向上聚集,並產生全區最高飽和度之高速水合物層與低速游離氣層。 本研究也從海底地震儀兩組水平分量資料之P-S轉換反射波解析水合物層的泊松比以探討岩石物理特性及流變性質。海底地震儀震測泊松比模型顯示位於OBS A4下方橫跨斷層兩側的水合物層泊松比(0.447)比較低,且其下方游離氣層泊松比(0.5)亦比較高。水合物層的低泊松比代表水合物含量高,而游離氣層的高泊松比則顯示可能有大量的游離氣依附並封存於基磐隆起造成的逆衝斷層、破裂帶與沉積盆地之中。
An integrated multi-channel seismic (MCS) and ocean-bottom seismometer (OBS) survey was conducted for exploring gas hydrates west of Kaoping Canyon off SW Taiwan in April, 2006. The total number of OBS stations is 35 with the spacing of about 500-1000 m. We used arrivals of the head wave, refraction and reflection on four-component OBS records to invert the P-wave velocity and interface of the hydrate-bearing sediments. Above the bottom-simulating reflector (BSR), the hydrates with a high P-wave velocity of 1.8-2.04 km/s and a thickness of about 100-150 m are imaged. Beneath the BSR, the free gas with a low P-wave velocity of 1.4-1.72 km/s and a thickness of about 30-110 m can be observed. In particular, the higher velocity (2.04 km/s, implying high saturation) of the hydrate layer and the lower velocity (1.4 km/s, implying large amount) of the free gas layer are seen below stations with strong geochemical signals. P-S and S-P reflected waves converted at BSR and seafloor were picked on two horizontal components of OBS data for inverting the Poisson’s ratios of hydrate and free gas layers. The lower Poisson’s ratio (0.447, implying high saturation) of the hydrate layer across a thrust fault and the higher Poisson’s ratio (0.5, implying large amount) of a free gas zone south of the thrust fault are imaged. According to the OBS models of P-wave velocity and Poisson’s ratio, we suggest that the high saturations of gas hydrates and free gas have been found in two anticlines formed by two basement rises, and gas hydrates may have migrated through two thrust faults north of these anticlines.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M94860005
http://ntour.ntou.edu.tw/ir/handle/987654321/15215
Appears in Collections:[應用地球科學研究所] 博碩士論文

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