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相關文獻
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題 名 | 臺灣西部地殼內地震剪力波的非均向性=Crustal Shear-Wave Anisotropy in Western Taiwan |
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作 者 | 陳美瑜; 張翠玉; 梁文宗; | 書刊名 | 經濟部中央地質調查所彙刊 |
卷 期 | 20 2007.07[民96.07] |
頁 次 | 頁53-69 |
分類號 | 354.4 |
關鍵詞 | 臺灣西部; 地殼; 非均向性; 剪力波的分離作用; Western Taiwan; Crust; Anisotropy; Shear-wave splitting; |
語 文 | 中文(Chinese) |
中文摘要 | 當地震剪力波(S波)通過非均向性層時,會分離成兩個不同極化方向的快、慢剪力波,以不同速率傳播,此稱為地震剪力波的分離作用。臺灣位於歐亞大陸板塊與菲律賓海板塊的交界,板塊間相互碰撞擠壓的力量使得地殼變形,許多具方向性的線性構造對應發生,如裂隙、斷層、葉理等,這些構造都有可能影響地震波速度而造成地殼內地震波傳的非均向性。本研究使用波形交對比法分析強震紀錄,觀測臺灣西部地殼內地震剪力波的非均向性,並更進一步探討在臺灣西部非均向性與區域構造及應力/應變場之間的關聯。目前測得沿海平原區域快S波極化方向大致與應力/應變場吻合。鄰近斷層與山脈快S波極化方向與時間差變化大,顯示這些區域非均向性側向變化顯著,而其快S波極化方向大致與山脈走向平行,應與麓山帶所發育的層面構造有關。由我們的分析結果推論,臺灣西部地區地殼非均向性主要存在於淺部地殼內。 |
英文摘要 | When seismic waves travel through an anisotropic media, they will propagate with different velocities depending both on their propagation and vibration direction. This causes the splitting of shear wave into the fast and slow propagation, and so called "shear-wave splitting". The fabrics that generate seismic anisotropy in the crust can have many causes, such as creaks, faults and/or foliation. Taiwan lies on the boundary between the Eurasia Plate and Philippine Sea Plate and is subject on the convergent mechanism between plates. The vigorous plates' collision affects the whole Taiwan island, and inevitable has generated the series of deformation structures in varied scales. In this study, we apply the waveform cross-correlation method on the CWB accelerograms acquired in western Taiwan to investigate the seismic anisotropy around the deformation front of the convergent system. The first image derived from the shear-wave splitting analysis reveals that the seismic anisotropy is strongly affected by local structures and stress/strain regime in western Taiwan. The fast direction corresponds to the compressive stress/strain trajectories in the coastal plain, whereas the fast direction and the delay time are varied across the fault zone or the mountain area. This indicates that the thickness of anisotropic layer or the intensity of anisotropy changes as the structure varies in space. The fast direction around the foothills area is generally parallel to the strike of the mountain. According to our results, the crustal anisotropy in western Taiwan region should exist in the upper crust. |
本系統中英文摘要資訊取自各篇刊載內容。