查詢結果分析
相關文獻
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頁籤選單縮合
題 名 | Geodynamic Implications of Present-Day Kinematics in the Southern Ryukyus=琉球島弧南端現今板塊運動在地體動力上的意義 |
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作 者 | 劉家瑄; | 書刊名 | 中國地質學會會刊 |
卷 期 | 41:4 1998.11[民87.11] |
頁 次 | 頁551-564 |
分類號 | 351.94 |
關鍵詞 | 全球定位系統; 板塊運動; 南琉球島弧; 弧前盆地; GPS; Kinematics; Southern Ryukyu arc; Forearc basin; |
語 文 | 英文(English) |
中文摘要 | 從最近收集來的GPS以及海洋地球物理資料,我們得以建立琉球隱沒系 統南端現今板塊運動方式,並提出其在地體動力上所引伸出的意義。相對於 南中國地塊,琉球島弧最西端的地塊(包括與那國島)向南移動的速率要比 臺灣東北部地塊的移動速率每年快1.4公分。位於花蓮東方海域的和平海盆 因而座落於臺灣東部和與那國島之間的一條南北走向的平移拉張帶之中。以 現今地塊移動的速率來計算,和平海盆很可能是在距今兩百萬年內經由一系 列南北走向呈雁行排列的右移斷層與伴隨的N40°E走向的正斷層活動所發展 出來的一個拉張盆地。另外,在琉球島弧南緣與那國島和波照間島之間有一 個呈N50°W走向的地塹,這個地塹的形成可能是最近四十萬年來與那國島地 塊和波照間島地塊以不同的速率相對於南中國地塊移動所造成的。事實上, 如果以現今琉球島弧南端地塊移動的速率來計算,南沖繩海槽有一半的擴張 量是在最近兩佰萬年內產生的。如果我們以123°30'E做為琉球島弧南端與那 國島地塊與波照間島地塊的分界,從板塊相對運動的三角向量分析我們可以 推算出,在123°30'E以東,菲律賓海板塊對琉球島弧的相對隱沒速率為N312° 方向每年10.5公分;在123°30'E以西則是N325°方向每年10.5公分。我們以 琉球海溝的走向為N275°來計算,板塊斜向聚合的角度在123°30'E以東及以 西分別為53°及40°。由於琉球海溝在122°40'E以西向北轉向,板塊斜向聚合 的角度隨之增加為60°。如果我們假設菲律賓海板塊斜向隱沒其滑動量的分 離度是0.5,則琉球弧前增積岩體(即耶亞瑪海脊)每年將以3至5公分的滑 動量朝臺灣移動。 |
英文摘要 | Both newly acquired GPS and structural data in the southern Ryukyu subduction zone allowed us to point out some first-order geodynamic implications of the present-day kinematics. Off Hualien, the Hoping Basin lies on a wide zone undergoing north- south transform motion and associated extension between NE Taiwan and the Yonaguni Island. Indeed, this westernmost segment of the Ryukyu Arc, which includes the Yonaguni Island, is moving southward 1.4 cm/yr faster than NE Taiwan with respect to South China. The basin could thus have developped as a pull- apart basin controlled by en-echelon N-S-trending right-lateral strike-slip faults and associated N40°E-trending normal faults during the last 2 m.y., based on present divergence rate. A N50°W-striking valley cutting the southern Ryukyu Arc slope between Yonaguni and Hateruma Islands is explained as a graben caused by the still ongoing differential motion between Yonaguni and Hateruma Ryukyu Arc segments, during the last 400,000 years. If we extrapolate back the present-day kinematics, about half of the southernmost Okinawa Trough might have been formed during the last 2 m.y. The convergence rate between the southern Ryukyu Arc and the Philippine Sea Plate has been estimated to be about 10.5 cm/yu in a direction of N312°east of 123°30'E, and N325°west of 123°30'E. The convergence obliquity is thus estimated to be about 40°and 53°, with respect to the N275° striking Ryukyu Trench, west and east of 123°30'E, respectively. The convergence obliquity increases to 60°west of 122°40'E, because of the northward turn of the trench close to Taiwan. The Ryukyu accretionary wedge (Yaeyama Ridge) can undergo about 3 to 5 cm/yr of transcurrent motion toward Taiwan assuming a mean degree of partitioning of 0.5. |
本系統中英文摘要資訊取自各篇刊載內容。